He LIKED me and I blew it. Can I get him back?

This guy at work really liked me and I was crazy about him, but we worked in the same department so I kept my distance. Now he moved to a different dept so it's perfectly safe, but this was months ago and I still want him, but he's a little chilly towards me. Can I turn it around??? Idk if he got a new gf or what he's doing, but he's not paying attention to me anymore. But I have the feeling I could pull it together, he shows a few small signs. Should I - and what should I do?? I can't forget him.