Why is this guy doing this? What should I do?

A couple days ago I told my friend that a liked him. He then said "You don't want a guy to hear you say that," And he walked away. I was confused so I didn't ask him what he meant. The next day he started to ignore me. To the point where if he saw walking down a hall at school. He'd turn around and make a detour around me. The next day I asked him why he was doing that and he said he'd heard that I wanted to make out with him or have him. I laughed it off and said I don't but he didn't believe me and is continuing to give me the cold shoulder. It kinda hurts that he's ignoring me since we were good friends before and I don't know what to do. Help?