Any method you use that involves physical means to control biting/nipping can result in escalating the behavior because it's reinforces the behavior- good or bad- because it elicits and emotional response from the dog.
Since the dog is already showing it's going to continue the behavior (and really all puppies do nip/bite) and get worse, your best bet is to reduce the emotional response by: 1) Standing up and ignoring the bahavior EVERY SINGLE TIME the dog does it. 2) Replace you with an appropriate thing to chew on (boodah velvet bone, carrot, frozen washcloth, rawhide, etc). 3) Pick pup up and seperate him from you for 2 minutes or until calm (repeat as needed). Do not say a word with any of these unless maybe when redirecting to an appropriate chew item. I have dogs that got wilder when I would say things in an excited tone so saying nothing was easier. You want to mimic the behavior state you want from them- calm, cool, collected is the key.
It does take time, but not too long to see results with these methods. I didn't yelp and say no with my dogs because that seemed to heighten their arrousal and did not discourage the behavior. I also didn't hold their mouths shut or press on their tongue because I don't want my dogs to learn that physical bullying is the way to get what you want. Granted I have a breed that's prone to thinking that way anyway, so I discourage physical correction of all types and even train my dogs to heel off leash before I put the leash on them. At this point in my dog's training, a leash is basically a safety net and not a way to force them where they need to go.
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Chelle and the rest of the crew including, but not limited to Kita and Taiko (the shiba inu wrestle maniacs), Adi (reserved and dignified tabby cat), and all 28 reptiles