I assume you've tried the standard exaggerated cry of pain when bit or nipped? If that isn't working I would try immediately slapping a muzzle on him then into the kennel for one or two minutes of 'no play' time. That is all the time it will take to make your point then repeat as necessary.
Remember he's a puppy and perseverence is necessary. A lengthy stay in the kennel does not teach anything - its the repetition.
Remember he's a puppy and perseverence is necessary. A lengthy stay in the kennel does not teach anything - its the repetition.