Do you hava any other dogs that Gunner plays with? Winnie had similar boo boos from playing rough with Jack. She then got Demodex. With that, she just had a couple of small bare spots (no hair) and at most a faint pink color to her skin. Caught early, Demodex isn't a big deal to treat. All dogs have the Demodex mites, their immune systems usually take care of it though. Let us know what it turns out to be!