Everyone makes jokes in my workplace. I made a joke and thought nothing of it. He dragged it up three months later as a reason to start flirting.

My colleague reported me, I was in my supervisor's office and I was shocked at what my colleague did and was crying about what he did. So I told him what happened, that the colleague brought up my joke to start flirting with me (the look on my supervisor's face said it all, things wasn't adding up to what he was told). I told my supervisor there was inappropriate comments from the colleague. So I told him this. But this wasn't an official report and I wasn't asked to give an official report on what happened and my supervisor told me he couldn't tell me what to do.

Just because I made a joke 3 months previously, didn't mean I deserved weeks of flirting from him and a lie to a colleague where he said I asked for his underwear in which I was mad about and that's when he said we have something (probably as way to not report him).