AGONY: My ex is my boyfriend's friend, do I tell him?

AGONY | LOVE & RELATIONSHIP

My boyfriend and I have been dating for about a year now and everything is going on well. We are really happy. There is just one problem.

About two months into the relationship, I met some of his friends and realized that one of them is someone I dated when I was much younger.

We acted like we had never met, but every once I wonder if I should have said something.

What would my boyfriend think if he found out? Should I tell him the truth or let sleeping dogs lie?