Hey babygai, cuddles to your pup from me!
woofgang is right as ever, and Lucy Thomas isn't (good on you for disagreeing!)...
Pup can learn as he is only young. I am not sure if it's a guy thing, but my partner likes to get our Collie all hyped-up, and it's not healthy. Staffs are pretty excitable too, so as woofgang says, you just need to be nice and calm, no raised voices, sudden, jumpy movements (as these can make you a target for your dog's nips or bites) or dashing around. Play is great for a dog, it just has to be the good kind of play!
I know I am only echoing woofgang here, but I just want to confirm that it worked for me too. As soon as pup nips, disengage completely from the game, ignore him (dogs HATE that!) and don't start the game again until he is calm and you are ready. Make sure your boyfriend does the same-I know it can be really hard to agree with a partner on training etc., but hopefully he is of the same mind as you and understands the importance of a well-trained dog.
I am so pleased you asked for advice. Staffs are so lovely and yet so negatively publicised. Keep up the good work :)
Let us know how you all get on.