Take the dominant role with the pup. Don’t leave it to Bo. I would begin with dominance exercises - lay the pup on his back and keep him still with your hands. I use the command “ahh” every time the pup moves and clamp him with my hands. Eventually you should be able to put the pup on its back or side and it won’t move until you use a release command. An “Ahh” should stop him if he moves. Next comes the “leave it” command which I’m sure you have on Bo. Use the nipping to introduce the “leave it” command. A little clip on the nose with the leave it might help with the reinforcement.
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