Well, I can see a black spot, but can't tell much other than that. Doesn't look as diffused as a bruise, so it's most likely some sort of infection or abscess. Figuring out just what is going to take a vet...who can take a sample and culture it, try to open it up and clean it out, or at least examine it much more closely. Some fungal infections will glow under a medical black light a vet should have. I'm afraid if you just dab some topical med on it nothing will change.