Swollen genital area in male bun. Please help

My bun bun is usually up to only one thing- destroying things, but yesterday he was sitting all quiet in a corner. I couldn't understand what was wrong so i picked him up and noticed his genital area is swollen. He has been eating like he normally does and is even flopping from time to time. I went to two vets today. The first one said it looks normal and told me to buy a packet of muesli(what an idiot) to lift his spirits. The second one said it might be a minor infection and gave me an antibiotic meant for dogs( i didn't give him that cuz i wasn't sure). Basically all the vets in my city are dumbos who only know how to treat dogs and very few know a thing or two about cats.
Please someone help me because i have no idea what to do.
Also i gave him a marigold flower today because i read somewhere that it helps heal wounds.

An infection is the most likely cause of the swelling. Do you know the name of the antibiotic the vet prescribed? If it's not a rabbit safe antibiotic, maybe you could ask for enrofloxacin(Baytril) or sulfamethoxazole/trimethoprim. Those would be the most common oral antibiotics prescribed for rabbits, and are considered rabbit safe. You may also want to request meloxicam to help with pain and inflammation. Dosing info in this link.
http://www.medirabbit.com/Safe_medication/Antibiotics/Safe_antibiotics.htm

And if your rabbit isn't eating very well, it's usually needed to start syringe feeding to keep the digestive tract moving so a rabbit doesn't develop an intestinal blockage. If you have Oxbow Critical Care rabbit food mix, that is what is commonly used, or you could make a mush out of your rabbits pellets soaked in warm water(make sure to make fresh every time). It's also important that they are getting enough water. If he's eating and drinking normally, syringe feeding isn't necessary, but if he's hardly eating or not eating at all because of the pain, syringe feeding is needed. How much to feed depends on how much he eats on his own. If he's not eating much at all, I would syringe feed 6-8ml per kg of body weight, every 4 hours. Syringe feeding needs to be done slowly and carefully, giving a rabbit time to chew and swallow, so they don't aspirate any of it into their lungs, which can cause pneumonia and be fatal.
https://rabbitwelfare.co.uk/rabbit-health/syringe-feeding-guide/

Another possible cause could be a tumor, and if this is what is going on you would need to find a vet experienced enough in rabbits to investigate this possibility and maybe neuter your rabbit.

Hi, thanks for your reply.
My bun bun was neutered in march this year. Do you still think that there could be a case of tumor if he's neutered?
He is eating his grass as usual but i reduced the amount of veggies today.
The medicine i got from the vet is called CEFPODOXIME PROXETIL ORAL SUSPENSION IP.
Should i give it to him?

This is the medicine i got from the vet

DO NOT give that antibiotic to your rabbit! Cephalosporin antibiotics are not safe to give to rabbits orally. Your rabbit may not even need an antibiotic anyways.

Ok. I thought by genital area you meant his testicles were swollen, so tumor ruled out. If it's his anus that is inflamed, it could be an infection or inflammation of some sort, particularly if his fecal poop has had any abnormalities(odd shaped, mucous, not pooping for a while). If it's his penis/urinary tract, it could be a urinary tract infection, or it could be calcium build up in the bladder. Have you noticed him not pooping for a while and acting uncomfortable, any blood or odd urine(thick and creamy or gritty, brown colored), any frequent peeing accidents or dribbling urine, or any odd behavior recently?

He likes to pee in all four corners of my room so i have one litter box in each corner. He also likes to pee on my bed, for months I've tried to make him not pee on my bed but nothing seems to work. Apart from all the above mentioned places he hasn't peed anywhere else.
He's been pooping normally and hesh pee also seems to be normal. I let him wet my bed sheet today to see his pee and it was the usual.
Do you think the swelling could be because of an injury maybe? He jumps around my room like crazy sometimes. Also sometimes he falls off my bed while binkying.
Or maybe his brother bit him there?
They fight sometimes but I've never seen his brother bite him there. His brother is also neutered and they're from the same litter.
PS I'm so grateful that you're taking the time to help me.

Since he seems to be eating and behaving normally, I think I would just keep an eye on him and check him tomorrow to see if it is still looking swollen. It could have just been some random inflammation and you'll find it's gone tomorrow. If it's still swollen tomorrow then maybe there is something going on, but without any obvious indications it's hard to know what exactly.

His swelling seems to be reducing gradually. I really hope its nothing.
Thanks a lot for your help