Sore hocks possibly bleeding?

I took my rabbit to the vet last week for his yearly check up. He was all healthy except the vet told me he had sore hocks on his feet. They weren't too bad im assuming because she didn't prescribe any ointment or bandages and he's been acting normal running around. He's free roam in my room which is carpet but his fur is fairly thin and she told me some rabbits can get them even from carpet so she suggested I get a kids play mat for him and they can heal on their own. I haven't had the chance to get them yet, but today I checked his feet again and there was a brown stain on his foot where one of his sore hocks are. I immediately called the vet but his doctor won't be in until Monday so she left a message, I also sent a photo of his foot. Do you think this looks like a blood stain? I moved his fur out the way to check the hocks but there didn't seem to be any open wound but maybe it's small and I missed it? I don't know what else it could be other than pee but I clean his litter box quite frequently and it's only on one foot. Also, I don't know if the vet will ask to see him again and take my word for it that his hocks are bleeding and prescribe him ointment so is there any negative effects treating sore hocks with ointment if they aren't open sore and in the first stages? Does anyone else have experience with treating sore hocks?

My late Herr Hase had sore hocks at one time, only noticed because of the blood stains on the floor. I got an ointmen from the vet, which was just a skin care stuff, nothing fancy. I fenced off all asphalt areas of my property, and put corrugated cardboard on the hard PVC flooring in my house for half a year - not pretty but good for their feet. I also got some baby socks, those with little rubber spots on the sole for traction, that did fit from coworkers: He rid himself of those more often than not. There are special socks made for rabbits with sore hocks. I think there was even ad here.
It healed off eventually, but other , not related problems started.

That looks like a stain, not related to the sore hocks. If the bald spots are not looking red/inflamed, then the best thing is indeed adjusting the flooring. No need for any treatment at that stage. Most carpet is too abrasive. Layers of soft towels and fleece blankets and duvets or soft mattress toppers are good. You want a surface where nails can dig in. Keeping bunny slim and nails short can also help. And encouraging exercise.