You have Phimosis, which in your age, the foreskin should still be forming so may be easy to treat.
Stretching exercises, when erect just
pull it back as far
as it will go and hold for 5 mins. Do this a few times daily.. in the shower helps, and you should see results within days/weeks. Could also try, if its possible to pull back a bit, pull it back, grab the glans( top cap of penis) with two fingers and roll the foreskin up over the two fingers as far as it will go (when the ring of skin
turns white). hold it there for 5 mins. Lubricant helps with this!. . It's fairly common, and this should help. Also try rubbing vitamin E around the top and inside the foreskin, which may help elasticate it. If it's more serious, you may need a preputialplasty (alternative to circumcision
but with no loss of looks, senstivity or anything, and is less painful with a fast recovery rate. With a preputialplasty:they make a small incision vertically then horizontally in your foreskin, and stitch it up to have more space for your glans to appear without a total circumcision. But with exercise for 5 minutes daily it will be ok.