Okay, this is something you need to get control of as soon as possible. Just yelping or moving away or scolding will not work, nor will "just" getting him tired. He needs to learn that there are things we can bite/chew, and things we cannot. First, I do hope you have plenty of ropes and chew toys around. Keep one with you at all times. Invest in some Kong toys, too. When the pup starts to get excited or seeming like he is about to nip, pick up a toy and place that in his mouth. Be consistent. Tell everyone in the family to do this. Work on obedience training. Simple "Sit" Down" and "stay" commands are vital! And then always, if he's getting exited, stop and run him through a set of commands.

He is a Labrador mix - they are retrievers. He *needs* to have something in his mouth to be happy much of the time! When you start a walk, give him a toy or even just a stick to carry. That will keep the mouth busy and the brain concentrating on doing something. I used to do this with a boss's poodle puppy, because if I didn't present her with a stick, she'd pick up someone's discarded cigarette butt or the like. It became part of our routine, and walks were much better for everyone.

Get him a chew/tug rope with multiple knots, he will be a big pup, so you need one that will hold up.

And do consider obedience classes, this will help you, and help him.

One of my favorite "tricks" for a teething pup is soaking a washcloth in chicken broth, twisting into a rope shape and freezing it like that. The "rope" will then be tastier than you, and the cold will soothe his gums, too.