Too big of an age difference???

So me (16) and my friend (20) had a thing about a year ago where he was my first kiss. We both go to the same sports club so every once in a while, he'll come home from college and we'll see each other. Ever since the thing we had last year, we've kinda avoided each other and pretended it never happened (once I sent him a "what are we" text after the incident, he said he really liked me but he didn't want to hide a relationship). But now, he's getting all flirty again. What do I do? He's a really cool dude but that age difference though....