I would do a conditioner treatment tonight (wet his hair and later it in white conditioner and use a metal nit comb through it and wipe it onto a white cloth) to see if he has any nits or eggs, and if he does, treat it; if not, do the same thing with the conditioner every 3-4 days for a few weeks, just to make sure he stays nit-free.
We just went through the whole lice debacle too, my niece had it and we weren't told until after my children had been playing with her for over a week (we were staying with them) and had gotten it off her. It has taken me almost a month to get them all nit free. FINALLY!!!