my pup was doing the same thing.I would give him a loud firm "NO" with a slap with paper.when he bites grab him by the bottom lip and mash,if it hurts him he learns that "NO" means just that.
he will grow out of it,but you have to stop him from bad habits in your way.be the dominat dog.look him right in the eys untill he give in,get closer and closer till he turns,never,never turn away your slef.that makes him think he is the dominate one.just be firm and consistant.over and over is the thing.