Early childhood prob. If you do npt remember how you got the scar then it must be something from your very early childhood. Ask your mom or dad they may throw some light. Other possible lesione could be early childhhod injury to your glans, injury from circumcision (if you had one!), removal of a cyst or from infection of the glans penis-balanitis and so on.
Penile scar. It's hard to determine what a scar is without an examination. If you were circumcised or had any history of trauma to the penis when young, it could be related to that. It's possible it could be related to a congenital condition where the urethral did not develop properly. What's more important is, does it cause you any problems? If it doesn't, don't worry about it.
Unclear. If you are concerned, I would recommend an evaluation by a board certified urologist or plastic surgeon.
A small scar? This really could be just a scar, perhaps from a zipper injury? These re more common than you might think.