I have two dogs. When we had the first one, 12 years ago, I had serious doubts about her behavior, it was so awful.
From the age of 7 weeks she bit me every day. (I'm sure you know how puppy teeth are like needles!) I tried my best to ignore it, gave her chews, plenty of toys, things to keep her occupied. No rough play, no tugging games and definitely no smacking.
Ignore the bad behaviour - praise the good.
When she was about 4 months old, the biting stopped. She is now 12 years old and has never growled or snapped at anyone and the only thing she has ever bitten was a mouse she found in the garden!
I learned a lot from having her and when we had our second dog two years later we had none of the problems we had with her.
Tell us more about what happened when your puppy bit your son - what were they doing at the time?