I have an uncut penis my penis's foreskin will com to pubic bone easily when flaccid but it will not come to my glans when errect is it normal?
Not being able to retract your foreskin when erect is very common but usually resolves around age 16 or so.
Unfortunately, there are many older men who did not know that it should retract. Nobody talks about their penis to another guy do they?
You can try to stretch your foreskin. Get an erection and pull down on the shaft skin so the glans spreads the opening OR use your fingers to spread the opening. It may help to do this in the shower as the warm water will soften the skin.
If you are much over 16 then see a doctor/urologist. There are some medications, steroids, that can help stretch the skin.