In the picture, it appears that the affected skin is bumpy and then there is quite a bit of redness around the edge. It’s possible that it could be a wart-like growth, but because of the amount of inflammation (causing the redness) going on, I would recommend taking Mac to the vet for a closer look. The vet will also look closely at all of Mac’s other skin (and mouth and other mucous membranes) to see if there are any other affected areas. They may be able to diagnose or have a better guess as to what’s going on, and discuss treatment options if any need to happen. Until he sees the vet, it would be helpful to have him wear an e-collar/cone so he can’t lick the area anymore. Licking will increase the inflammation and can skew how the vet evaluates the area. Thanks for selecting Petco Pet Education Center, formerly Petcoach!