Do I tell my boyfriend I slept with a mutual friend?

So this happened before my bf & I met. We've only been together a couple months. We have a small friend group of about 7 people, plus two acquaintances that sometime hang out with our main group. Of the 7 people in our group, 6 of us are couples. The "odd guy out" (Ogo for short) is the one I slept with before I even met my bf & became part of this friend group. I was the one that introduced Ogo to the group after I met all them. Ogo & I stopped only slept together once or twice, over half a year before my bf & I met. I just feel like maybe he has a right to know, because Ogo is part of our group? But at the same time idk if it even matters cause it was so long ago && before I was with bf. thoughts??