I have always thinking about a boy 3 years younger than me... how can I stop?

I can't meet him anymore, we were in a 2-days-and-1-night camp and I had a big big crush on him. I'm 18 nor but he's somewhere about 14 or 15 years old. I know I stand no chance to get a relationship with him, but I just can't get over him. He is obviously doesn't know and even if he knew, he would not care either because we live in different states... I know it's wrong to think about him. I just move so I have no friend... What should I do?