When did he start biting you? Do you leash him when going outdoor?
Normally, a puppy under 1 year old will chew or bite because of teething. Owners should offer toys or sticks but avoid playing the pup with your hands. He could regard your hands as his toys and remember firmly, so you need to take some measures to correct this bad habit. You could search relative articles on google, such as
this one.
What's more, remember to leash your dog while walking. When he is ready to bite your hands, say "no" angrily but don't blame. If he stops, give him some toys or treats. Take him to
dog-friendly stores or parks until he has corrected the bad habit, in case of bitting strangers or canines.