Thanks for using Petco Pet Education Center, formerly Petcoach! This could be due to ringworm. This could also be just a focal skin bacterial infection, among other possibilities. I recommend that you have Fawkes evaluated by your veterinarian for further assessment and treatment. They would be able to check for these possibilities and treat accordingly. Ringworm can be transmitted to humans so just in case this is what is going with Fawkes, wear gloves when handling this lesion. Good luck and best wishes!