Apart from keeping it clean and dry and seeing a vet, no. I'm not so savvy with treating illnesses, I might try some stuff if I were in that position, but that would be pure guesswork, not something I would give as advice.
If it's just inflamed from being stopped up, now that it's cleaned off usually the inflammation goes down and the rabbit is fine, provided the mushy poop issue is dealt with and no prolapse has occurred . If it's not just inflammation but there is an actual infection or a prolapsed rectum, you will need to get your bun to an experienced rabbit vet for the proper rabbit safe antibiotic (eg. baytril) and necessary treatment .
To help clear up mushy poop issues, I cut out any high carb/sugary foods from the diet, reduce pellet amounts, and free feed a good quality grass hay (no mold or noxious weeds ), also ensuring the hay is being consumed really well. Mushy poop is caused by an imbalance in the gut flora and grass hay is usually the best thing for getting it back in balance.
I had same with 3 of 5 babies they were about maybe less than one week their mom was too stressed and didn't clean them so they had their genitals blocked with poos and it looked pretty bad when I removed them. I just cleaned with warm water (you did already), I used herbal teas to rinse them with a cotton wool pad a few times a day, hold for a few minutes and then dried with paper towel. I don't use antibiotics unless there's no other way, I don't remember now probably sage tea or chamomile, even if you have black or green tea (I don't use teabags only loose teas) they are all antibacterial, especially sage is very strong and wounds healing fast.
Babies grew up and now are 9 months old, took a few days to heal but first looked horribly I was really scared.
I think I know what it is! It might be mucosis enteritus. My very first litter of babies got it. It smelled terrible and after a while green mucus started coming out. The best chance u have is put probiotics in water and if she’s not drinking yet then syringe her some water. You will also need to find some antibiotics. The antibiotics will keep the baby alive long enough for the probiotics to work.
Sometimes with baby rabbits they get feces stuck... looks like it gets stuck in 'the wrong hole' as well. I haven't seen that happen in a few years, and it happened mostly with my Harlequins, not my himalayans, but once I cleaned it out the swelling would usually go down
Once you have it clean I would keep an eye on it and make sure it stays dry. If the inflammation doesn't go down in a day or two I would contact a vet. Baby bunnies are very small and very sensitive to most medicines so there isn't much you can do a lot of the time except keep them clean