You have a problem.
Your pup was much, much too young to be separated from a mother and its siblings. In most states it is against the law to sell a pup before the age of 8 weeks.
The mother dog and its siblings teach the pup to control its bite reflex. This is very important because it is how the pup learns not to bite too hard and to control his bite.
With a normal pup of 10 weeks a loud yelp from the human is sufficient to make the pup release. I would consult the vet and get the name of a professional you can work with to socialize your dog as soon as it gets it final puppy shots. I also recommend when it finishes its shots starting with puppy classes and keep on going to get the dog properly socialized.
I hope one of the rescue people on this site may have had experience with unsocialized pups separated too soon and can give you more detailed ideas to deal with the biting. One thing you don't want to do is hold the dog, allow it on a level with you. You do not want to hit it for biting. Use loud yelps, like another pup.
I also recommend crate training and making it the place where the pup sleeps, eats and gets all treats and stays when you cannot directly supervise it. Until a pup is completely housebroken and understands basic commands, like sit, down, off and coming to his name, I like to keep them right with me. At his age I would probably have a lead looped on my belt so he had to stay with me. A light correction with the lead and a yelp would stop any biting. The puppy's bones and neck are very fragile until 6 to 8 months of age so it doesn't take much to get his attention. You just want to mimic the mama dog's corrective nip.
By the way, most rescue people crate train their dogs. It becomes their den. When they earn more freedom they will retreat there to escape the children or just nap. My dog has earned his freedom at 2 yrs and the crate door is open so he can come and go at will. He naps in there and sleeps, eats and gets treats in it. It's like a dog house, but it is in the center of activity in the house.
If you haven't taken Cesar's Sessions, I strongly recommend you do so immediately and go directly to the new puppy section.
Establishing that you are pack leader and practicing NILIF (nothing in life is free) is going to be essential for this pup to grow into a balanced individual.
He shall be everything humanity strives to be: Honest, Loyal, Kind in Heart, and Strong in Spirit. Therefore, you shall call him Partner and Best Friend."
Author Unknown