Awww Anna that looks so awful. A couple of years ago I broke up an almost fight between my German Shepherd and a Rotti foster I had. Simon was not at all happy about Baby Girl being in his backyard and when he jumped up to let her know I grabbed his collar not thinking. He then turned around and got a nice chunk out of my thumb(my fingernail ended up falling off). I don't think he realized I had grabbed him and the only thing on his mind at the moment was letting that dog know she was in his space. He was very sorry afterward and no we did not rehome him because of it. We just made sure no more fosters were around him or in the backyard at the same time as him.