I fucked up - need advice!

So he has been my boyfriend for a months now he is the first guys that I have been with since my ex and I broke up 10 months ago.

I did see one person that was friends with my sister before my new bf but very briefly. We didn’t sleep together that’s how brief it was.

I told my current boyfriend that I did sleep with him so I didn’t seem like a weirdo that hasn’t gotten over their ex.

And now we are going away for the weekend and he is the guy that I was briefly seeing is going to be there.

I need to tell him that he is going to be there. Do I tell him that I was lying about sleeping with him? Wtf do I do? I feel like such an idiot!

I hope this makes sense