What should l do?

Okay, so l told this guy, who was a very good friend of mine, that l don't reciprocate his feelings (as he later confessed that he wanna be more than friends) and now he completely ignores me and like I don't know, maybe even talk shit about me behind my back, l feel bad cause we were very very good friends and l didn't wanna lose him, but this is so not justified, l can't force this thing, was l wrong for clearing myself?
What should l do?
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