I agree with the others here. Talk to your colleague.

You say alcohol isn't an excuse, but you wouldn't have said it if you weren't drunk. And you weren't the only one drunk there.

The fact you knew he was gay makes me wonder if it wasn't a secret, that at least some of your colleagues already knew. How did you find out?

And he laughed it off. Is he the kind of guy to laugh things off like this? If so, he's probably okay with it. Some people are just easygoing and wouldn't give this another thought.

Talk to your colleague. If you self-report to HR, almost guaranteed they're going to start an investigation that will likely end up in some form of disciplinary action.