Incoming Challenge: I have run into my Ex and things got out of hands - What should I do?

I have recently met my ex at a party,

we haven’t seen each other for a while and a party was a really good one. We ended up having a great time, talking about the old times, drinking, dancing and we ended up sleeping together.

The next day was pretty awkward, as we didn’t really know what to say to each other. I am not sure if it meant anything, or if it was just a mistake and I should forget that it ever happened. I wouldn’t like my ex to feel offended that I never said or done anything. I must admit that I can’t stop thinking about her. Could you advise me on how to approach that tricky situation?