Should I let my boyfriend take his ex lover to a concert with him without me?

Ok so a few weeks ago I went to a concert with my boyfriend and a few of his friends. There was a band playing before the actual band and he was talking to the crowd etc and he was saying how you should stay sad or angry at things. He said "if you sleep with your friends girlfriend it's ok to feel bad for a while but don't feel bad forever." We all laughed because I knew my boyfriend had slept with his friend girlffeidnd ( not ex girlfriend) I was ok with that. And come to find out the girl who drove all of us to the concert was that girl. He didn't tell me who she was until a few days later. I felt a bit sad. And now he's going to see Dave Chappell and possibly radiohead without me wich I'm ok with. But now he's telling me that the girl he slept with wants to go with him. And he asked me if it was ok if he could take her. I know they'll both be drinking and that's how they ended up fucking in the first place. So should I let him. What do you guys think?