I have an issue... please help...

My coworker recently showed up to work on Monday with 2 hickeys on his neck and he’s basically like my bestfriend and I kept teasing him about them because he didn’t want to say who gave them to him even though we all thought his ex gave them to him since they like to fool around. He now texts me that his brother thinks it was me and to tell me that its over. I have my own relationship of 7 months why would I go and do that. I get it him and I are close but I wouldn’t do that. Should I tell my boyfriend. My boyfriend and him are also bestfriends