He likes me! What do I do now?

Don't worry about the girl.can you just go up to him and talk to him? people get hung up on this stupid idea of 'asking out.' The reality of it all is that only makes the experience more stressful; thus, I always find it easier to just go and casually talk tot he person,and eventually you can casually say, let's go get coffee, lunch, dinner, whatever; that way now you are not asking out, but basically you're hanging out, which eventually leads to 'going out.' :)

So if you can just go up to him and make talk, that would be a start; if you give him attention, then the other girl is irrelevant.