Here’s a quote from:
If you watch a group of puppies playing, you’ll see plenty of chasing, pouncing and wrestling. Puppies also bite each other all over. Every now and then, a pup will bite his playmate too hard. The victim of the painful bite yelps and usually stops playing. The offender is often taken aback by the yelp and also stops playing for a moment. However, pretty soon, both playmates are back in the game. Through this kind of interaction, puppies learn to control the intensity of their bites so that no one gets hurt and the play can continue without interruption. If puppies can learn how to be gentle from each other, they can also learn the same lesson from people.
My dog no longer bites to break skin. I think that is how she learned, when I “yelped” and stopped interacting to nurse the bleeding. You don’t want to let it go till you get an injury. You could try saying a firm No (yelp), then ignore the puppy for a bit (stop playing a minute or two). See if the puppy gets the message. See alsoon Cesar’s Way.
Or you may find this video helpful: How to stop a puppy from biting in six easy steps: https://www.youtube.com/watch?v=NESkFolorqA