Looks a little like the start of scalerot or some other infection.
I'd move him onto a paper substrate and clean it a little.
And, because it is inflaming soft tissue I'd ask the vets advice about a course of anti-biotics.
dr del
thanks for the quick reply! I moved him to paper already and have been giving him warm baths every once in a while. I'm changing the paper as soon as I see any soil on it. I'll keep a closer eye on it, I don't want scalerot!!!