Comment: Judging from the pic

it must've been a pitbull. LOL sorry man couldn't resist.

I think you're mostly getting flak from your statements of putting the dog down, specially considering that "bite", which judging solely from the picture, looks like a bruise from a bite that DIDN'T break skin. Regardless of that, whether minor or not, it's still an injury, and it's up to you to document it if you feel you want to take this any further legally.

People are jumping all over you, but if you would have kicked that dog in order to defend yourself, people would probably be crucifying you as well for kicking a small defenseless doggie. It is what it is.