Unless he's feeling awkward about it and calls you up on it, I see no reason to make a thing out of it. Unless he's an egocentric flamin mongrel he's probably also aware that you might be feeling awkward about your in jest comments over the years. My personal view outside of the humour I post in here is that sexuality doesn't change what that person is to me, no more so than what kinky things a heterosexual person does with their wife in their own time that's also of no consequence to me. Sexuality is just another characteristic of the person - skin colour, big ears, tall or short, shy, intelligent or dumb. I therefore don't believe it should be off limits for jokes or mucking around. My brother is gay and I still pay him out with those words on occasion, not because he's gay but because I'd say them to anyone else too. Him coming out doesn't change this because I don't think sexuality should impact or change how you treat someone either. If he said that it offended him, I would be more sensitive to it around him just like I would anything else I say that offends people.But I would probably also engage in a discussion about my other view on gay slurs in casual conversation: I think that once upon a time they were used exclusively as an insult with the implied connotation that a homosexual was inferior or different in an unacceptable way (and sometimes still are used this way), however the more common use of these words as insults these days, particularly amongst teenage guys, has its own meaning which is far removed from the gay bashing it used to be. Consider that many teenagers using such words don't even know the full extent of their meaning. This is why I'm not apologetic for any instance of using such words when my intention is not to hate on gays.
However - like anything else I say, if someone were to take offence I might be more sensitive about it afterwards (after explaining my viewpoint), not because I necessarily agree with them, but simply because I'm not a total flamin mongrel and I'm more for keeping the peace.
I also wouldn't retrospectively apologise for what I've said not knowing they have taken offence to it - if someone takes offence to something at the time, the it is up to them to call you up on it then and there, or else they are more or less condoning it to continue by way of you thinking they are okay with it. People can't change if you don't give them opportunity to or the boundaries to play in. I might be more sensitive towards a topic from there on if someone has made it clear they are offended by it, but certainly wouldn't feel I've wronged them in the past.
tl;dr: I don't hate fags