It is fun! He bites, the bitee squeals and make a great noise - it is fun!
That being said, my son went through this about a thousand years ago (okay, only 14, but it *seems* like 1,000). I would tap him gently on the nose and firmly say "No bite". Consistently and every time his little mouth would open and he would lunge for me with those lovely new teeth. Sometimes I could tap him before he bit. He got the message and the biting stopped.
My cousin had a toddler that bit - I mean like a 2 1/2 year old - no one knew what to do about it - regular methods didn't work - the kid was a biter, family shrug. I was about 17 and visiting them enjoying a large Italian family dinner, when the little rascal toddled up to me, leaned in and bit the crud out of my arm leaving a perfect imprint of his very healthy teeth. I calmly leaned over and bit him back. I have never seen such a look of surprise on such a little face. Um, I was told that he never bit anyone again. And I must say, he remembered me when I went back to visit a few years later. LOL Yes, I was younger and had zero experience with children. Which is why I never bit my own child back.
So, try tapping his nose, firm "No" and if all else fails, bite him :)
Basically, it is a new thing for him, it is fun, and like everything else, you need to be patient and teach him not to do it.
Good Luck
God Bless