Enter thru Here 🚺

My SO and I were getting a bit frisky. He knows that I do not want to have sex yet. I'm still young and just about to start finishing school and make a career, and he is so cool with that and respects it (one of the reasons why I love him). He was trying to put his finger in me (which is ok, for the time being) and I don't know why, but it kinda started to hurt (it stung) and I tried to move away. I keep thinking about it. He tells me not to worry because it happens, but it bothers me 24/7. Is it normal? He said lube should help. Is that true? HELP! 🆘