So tell him that. If he has legitimate feelings for you and was actually a friend, he'll stick around. If you explain that it really is just the timing, he'll probably be willing to wait. And if he is willing, then you know you have someone that actually cares and isn't just acting on initial attraction alone.
The major issue though is to not end up stringing him along. If after a certain period, you realize that it's not just about the timing, you should let him know so that he doesn't miss something else because he still thinks he's got a chance for more with you.
I hope that he turns out to be mature enough to handle his feelings and that you two work out, whether that be just as friends or as something more.