Puppys only have their mouths to explore the world with and they have to be taught not to use them inappropriately. Yelping, and time outs are effective if done consistently. With my pups I also used to stick one of their feet in their mouth if they were biting me. They would bite themselves and realize that that hurt. I have never had one of my own dogs draw blood on me.
As for tug games - no need to stop those. On the contrary, I encourage you to continue tug games. Tug games were the life and sole of a puppys life in the puppy pen with his litter mates. Tug games are the precursor to teaching retrieve along with "give". Important though that you do let the pup win from time to time. Also important that you decide when the game stops.
Just be careful when he does start losing those puppy teeth. If you pull a tooth out you may destroy his love of the game.
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