At 7 weeks puppies bite and nip and mouth. Use the advice of The Bite Stops Here. It will take days or yours and mine cases (I've an 11 week old puppy) weeks. I've discovered the ignoring thing really works. I don't mean let the dog continuously chew on you, we do the "Looking for Rain" method where we stand still, cross our arms over our chests and look at the ceiling until the pup gets bored. However you've got to be consistent. There is no point in scolding a puppy, its an infant at that age. Distract, or redirect. Make sure the puppy has plenty of things appropriate to chew on, and make sure the puppy's needs are met, food, water, potty or may need a nap, puppies often mouth and nip when they need something. At this age we ignore bad behaviors or use "eh, eh," like you would a baby.
Edit: On a side note, 7 weeks old should still be with mom and litter mates. Puppies learn bite inhibition best from them.
A very important distinction before this thread continues. Is he "nipping" or "biting"? bite = an attempt to break the skin or damage. nip = a lighter bite, may still hurt but doesn't break the skin.
There is a "bite stops here" sticky you should read. While I have no experience with young puppies (and 7 weeks sounds a bit young) but would assume it's playfulness. As far as my older dog (1.5 years at the time), it's not so much about scolding but rather showing that bite/nip = end of playtime.