He is gorgeous!
Looks like it might be a bite or access that has drained, crusted over, and then become infected/inflamed around the edges. When the butlers I take in have wounds swollen like this, infection often appears as a whitish pimple like area at the apex of the swelling. Keeping the area moist w ointment seems to encourage the infection to come up to where it can drain. (The silvadine ointment you gave me is great for this.)

I hope he conquors this- he's abeautiful snappy looking guy.