I don't know what to tell you except not to worry if you don't see injury. You may just have a bossy breaches on your hands who thinks he oughta be in charge of who is where and who has what, etc. We had one like that. What we did is hold him firmly but gently and turn him on his back and kept him there until he stopped struggling, it's something that was recommended to me for bossy puppies. Basically he has to know that he gets what he wants by being calm and sweet not by being a bossy bully. Or at least if it's the same thing that was going on with ours. I had to do that with Boris because he thought he was the boss of everybody.