Puppies are capable of learning simple commands from a very young age but don’t try to give your puppy a meaningful training session if he is tired, highly excited or busy exploring. You need his full attention, otherwise you’re wasting your time. You can build up to training sessions in more distracting environments once your puppy is reliably responding to your commands at home.
As part of your puppy’s training, then, you should do everything you can to ensure that your puppy can’t get into trouble in the first place. That way you can avoid giving your puppy lots of ‘negative’ attention which might inadvertently encourage his bad behaviour. For example, if you use a crate, or confine your puppy to one room of the house, he is far less likely to get into trouble chewing something he shouldn’t, or peeing somewhere he shouldn’t.
When you're playing with toys it's the same thing: his teeth mustn't ever touch your hand. If they do you say "Ouch!", kind of the same way his little mates would, and turn away from him. So if you feel his teeth on your hand at all you let him know with a little "Ouh!", turn away and let the game stops for a few seconds. Make sure to speak up every time he bites too hard so that your puppy can learn your threshold for what is acceptable and what isn't. Then go back and play again but he has to remember not to use his teeth and to be more careful next time. Is A Harness Or Collar Better For A Dog ?
It's normal and even cute when your puppy nibbles and even lunges at your hand. Since your puppy has been exposed to only other puppies in the litter who naturally play with mouthing and biting, it would make perfect sense why he would assume that playing with you wouldn't be different. But as they grow and their bodies become stronger, what was once cute nibbling eventually turns into uncomfortable or even dangerous rough playing bites.