Is it childish to ignore someone who rejected you?

I have a male acquaintance from home, I've never really known him very well but as we both go to the same riding club I see him quite often and am good friends with a lot of his good friends. It's a big riding club with many people from my old school, and I've been there for quite a few years so they make up a large part of my social circle. I used to really fancy him, and he'd be quite flirtatious back, though often "hot and cold." Like, one minute, he'd be winking at me and saying stuff and even just constantly watching me to the point it got embarrassing, next he'd be talking loudly in my earshot about all the girls he'd slept with or getting touchy feely with one of my friends. However, last summer before we all went back to uni I told him I liked him anyway, and he said he had a girlfriend at uni so of course I didn't try to take it any further. I didn't see him for ages after that, but now I've been seeing him a lot again around recently at parties and such. I got over him completely, but now he's always smiling at me and watching me and coming up to whichever group of friends I'm in at a party. I haven't spoken to him once apart from saying hi, and would rather just ignore him; maybe he's just being friendly but I feel like he is a bit of a player and he never seemed to care all that much for me. Also, he (and most of my other friends who know him) have graduated as have I, so we'll all be at home for a while and I still have to see him :S Am I being childish here, or is this an OK thing to do? Why can't he just leave me alone too? I hate it when he stares at me. Even if he doesn't have a girlfriend anymore (I don't know if he does or not) it is really rude.

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