Background:
This situation is a little bit sensitive. Few days ago I was in restroom at my company, and just went about my business. Then one guy came in to the next urinal (restroom is kind of small, but we have a divider between them). Everything was silent as normal, suddenly he, well, farted so loud. And I just bursted into laughters, like hysterical laughter. I know it's not nice, it's bad, but it was funny at that moment I couldn't help myself. (It is like some Just For Laughs Gags episode)
So I looked up to see who this guy was, and to make it worse, this guy happened to be my big boss. And to make it even 'worser', he is around 20 years my senior. If he was my age, we could make a joke about it and shake it off. But he is my boss, I didn't know how to react. And you know how it is, when you are laughing so hard but you try to stop. So I said 'Sorry' and I walked out of the restroom real fast.
Situation
Now, my boss is very nice and all. But since the incident, he is kind of tense and uncomfortable around me. Like, when we have meetings, his answers to me are short, not rude or anything, but not like the way he usually is. And for me, after that incident, I just talk to him very normal like before (as my colleagues describe about me like an easy-going, friendly and respectful person).
I don't know how to shake this thing off with him. I can't and don't want to come up to him and say 'I'm very sorry about the embarrassing situation the other day ...'. Should I just let it like that and hope with time, it will eventually go away? I just don't want my boss to think negative about me just because of, well, this awkward situation.