Don't want to make you panic but yes, it's possible. Relatively unlikely but still one of those days where you would normally use protection. If you absolutely do not want to be pregnant (and this happened in the last 48 hours) you might want to think about the morning after pill.
If it wouldn't be a huge disaster then I'd just wait it out, seeing as your chances are quite small. But then if it was me I'd start taking folic acid and not drink alcohol until I knew for sure, just in case.
Hope you get the result you want!