I didn't know I fooled around with this guy's husband
How did you not know that he was married?
I didn't ask to them about it and I didn't care either.
Messing around with someone's spouse is serious and it's incorrect to get into that kind of relationship. Find someone who is single and drop this guy.
I don't care, I'll never see him again.
Take this as a good life lesson then and never do it again. You should not get involved with someone that has a spouse, or even a significant other.