I am 15 and my foreskin erect or not wil. Not pull back much more than half and inch is this a problem?
It's NORMAL, until about age 16 or so, for your foreskin to not retract fully.
Start stretching it. You can use your fingers to spread the opening or get an erection and pull down on the shaft skin so that the glans spreads the opening.
The more often you do it the sooner your foreskin will retract. Skin grows under tension.
You may find it easier to do in the shower, the warm water will help soften the skin. Don't hurt yourself. There may be some discomfort though.
Hope it helps.