What Causes Pain During Vaginal Penetration?

Hello, I am and 18 year old woman and have recently become sexually active. The past day or so however, any type of vaginal penetration has been very painful. My boyfriend and I had sex (literally) for about an hour yesterday morning, and the pain started near the end when I was rather dry. My question is, could this have caused vaginal tearing which would be the reason for my current pain? The lining of my vagina feels like it has been rubbed with sandpaper, it is not a burning/itching sensation which leads me to think it may not be an infection.