Raise preflop. If he calls, the only hands you have beat is TT and JJ, and of course splitting with another AK. AA, KK, QQ and AQs has you beat. Nits don't raise many other hands and would definately not call a reraise with anything else. And they rarely if ever two barrel with air.
It is very easy to fold against a nit if you have stats on him.

If you don't want to raise preflop then do it on the flop. If the nit has AK too he might want to get a cheap showdown and check it through due to your raise. If he has TT or JJ he will fold, he might even fold AK as well if he is a supernit with constant set paranoia. If he calls and bets the turn, fold. If he comes over the top, fold.