I can only retract my foreskin behind the glans when my penis is flaccid and not erect,it hurts if i force it. i only had sex once and when i first had intercourse my foreskin automatically went behind the glans. (should i be worried?) it hurt a bit?

It is imperative that you see a doctor, preferably a urologist for evaluation and treatment. Do not force the foreskin back. Get HPV vaccine.

Do not force it. retract the foreskin well lubricated by cortisone cream as far back as comfortable several times a day (make sure to pull it forwards when done) try this for a few weeks and your foreskin will become supple and pliable. If not the other choice is a circumcision. You can do it