Unfortunately only the vet will be able to tell you for sure - skin issues are incredibly difficult to impossible to diagnose visually. This is one of the reasons the forum doesn't allow members to attempt to guess at diagnoses or give advice for medical conditions that haven't been seen by a veterinary professional - it's very easy for someone to offer well-meaning advice that winds up hurting your pup or delaying treatment. Good luck, and I hope it's nothing serious! Sounds like your pup has enough going on already, poor guy.