TMI: It didn't fit!

I'm gutted okay, my SO and I were going to have sex last night and as he was trying to put it in I was in extreme physical pain. I'm a virgin, so ofc I started freaking out because he wasn't fitting, and even my SO says he's not that big. What do I do? I don't want to leave him but if I can't have sex with him I feel like he'd be better off with someone that can. Please comment 😭