What an awkward and difficult situation for everyone involved. I'm so sorry that your sister's husband had the lack of taste and decency to say something like that out loud. It was hurtful to his wife, and he had to know going in that it would be.
I am curious as to why you think you provoked this. Did you say or do something that you feel badly about? You say your sister didn't talk to you that day either. Did you think you were also to blame?
My suggestion would be to ask your sister what she's comfortable with right now. Clearly, you and she have talked since it happened, so the air should be somewhat cleared, at least between the two of you. Probably the best thing for all involved would be if everyone could leave the situation between your sister and her husband and just go on about their business like it never happened. That would mean that you'd go to family get-togethers just like normal, and everyone would act like grownups. You certainly shouldn't avoid hanging out with them -- to me, that just makes a bigger deal of it.
What do you think?