My puppy's 8 months too, and he does the same thing! Except I thing he's probably even worse, because he nips my older dog in a way that makes it seem like he's doing it with aggressive intentions. He actually lunges himself at her (she's a dane, so there's little surface area that he can reach if he stays grounded, hahah) and will grab hold of her skin and refuse to let go.
She's actually been very patient and will just bare her teeth and growl at him, but if I were her, I probably would not be so tolerant! He's got tiny little teeth but they're very sharp and he's drawn blood on my poor dane a handful of time. We're tried putting him in his crate as a time out, but he'll just come back and walk around cautiously for a bit, then go back to biting.
