If he had still been with his litter brothers and sisters this is how he would have been behaving playing and learning now - the difference being that the mum and litter would have kept him is his place - he doesn't know he is biting too hard - as someone else has said i fear he left his breeder too soon - BUT - no major problems - just try not to encouragew it with playing - and just a firm no sould suffice during this early stage
regards
sue