With some dogs, squeeling or yelling, "ouch" doesn't deter them, but makes them think you're playing. I know it works with some, but not others. When you put your hand over the dog's mouth, he thought you were playing too probably. So, just plain walking away or removing the dog from your area (if he's attached to your heels) without emotion is best. He wants to play and chew so removing that as a payoff is the only thing to do. (Hey, I'm a poet) But do replace your body with a chew toy. And then praise when he's chewing on his bone or whatever. And just remember when he is "behaving," to praise him and maybe give a treat. Show him what behavior he does do that WILL bring a favorable response from you. You can say, "NO BITE" and then walk away. He'll learn what those words mean. Some people don't do anything negative and some do. But the mere speaking or further looking at him is often attention enough...a payoff. But, that's up to you. But at any rate, the most important thing is to praise him when he's not biting and able to play nicely.
And eventually, if you're consistant he'll grow out of it. He is teething so something to relieve that helps too. A rag soaked in tea and then frozen helps sometimes. But supervise and watch out that he doesn't break off any strings and swallow them. (dangerous) He should only just have it for a short time. Like Saje said, a frozen carrot might be hard enough and that cold might relieve the pain of teething. That's a great idea. Good luck.
