Some guys have foreskins that have tips that are too narrow to pass back over the penis head. These foreskins may be gently stretched over a period of time to cause them to widen. When your penis is erect, gently pull your foreskin back against the head of the penis. As the head attempts to pass through the foreskin it will stretch the skin a little. Do this every day and in a few weeks or months your foreskin will widen and you will be able to retract your foreskin. Do NOT force retraction.
It works by tissue expansion. Stretching skin induces “mitosis” which is a word that means “division of cells”. New skin cells are formed and the skin expands. The increase in size is permanent. Be patient and let mitosis do its work.
At age 15, your foreskin is still developing. If you do the stretching exercises above, you will eventually get a fully retractable foreskin.
The notion that a man’s foreskin will retract when he gets an erection is only partially true. A foreskin will only retract if the tip of the foreskin is wide enough to pass over the head of the penis. A foreskin will only retract if it is shorter than the erect penis. A foreskin that is longer than the erect penis will never retract automatically but may be retracted manually, provided it the tip is wide enough to pass over the head of the erect penis.
Most boys and many adolescents have foreskins with tips that are too narrow to retract. By age 18, the foreskin should be loose enough to retract.
When a long foreskin is manually retracted, it gathers in folds at the base of the penis. The folds want to unfold and push the foreskin forward back to its normal position. A long foreskin is likely to slide/roll forward to recover and protect the glans penis when it is released. Some men simply cannot keep the foreskin retracted. This is not considered to be a problem.
The long foreskin provides superior protection to the head of the penis. Moreover, the ancient Greeks considered a long, tapering foreskin to be a sign of male beauty. The long tip is called the akroposthion.
The long foreskin may improve the sexual experience because of its superior gliding action.