I caught him doing it again as he was falling asleep tonight. Grrrr.
It seems like all the nail-biters here are saying "don't bother... nothing will work and he'll eventually (maybe) outgrow it," while all the non-biters are saying "use this, try that, rub this on his hands, dunk his head in a toilet, etc..."
I think for now I'll listen to those who are more experienced with nail biting than myself and just let it be, since his hands are still in pretty good shape. Heck, maybe it's a blessing! I'll never have to pin him down to cut his nails again
(If he starts getting as bad as his Daddy or his Grandma, however, then I will have to break out the Bitrex/artichokes/hotsauce/toilet/straight jacket, etc.)
Thanks for the advice