Most vagina's are only about 4/5 inches long, whereas most erect penises are around 6 inches.
When you're turned on your vag can get about 2/3 inches longer, when you're not turned on an average sized penis should still fit without too much hassle and lube and the friction will help you to accommodate.
He unfortunately was too long for you and that was that. There is nothing wrong with you, you're probably quite short inside unaroused, whereas he's quite long while aroused. It's probably best you don't see him again if he's going to pain you.
To be honest I struggle with length in bookings too, which is something I rarely experience in my real life.