Just found this on ddog. He was licking it but I don’t think it’s bothered him much. Dh now says last night he was licking there and whimpering slightly but didn’t think to check or mention it 
Should I put something on it? Take him to the vets? Or leave it and see what happens. He could have caught it in the woods while leaping over stuff. Not sure it looks like a cut, bump or spot type thing though.
He’s still full of energy and ball chasing like a nutter.