Scarleteen

I would like to have an opinion.
What could be the problem for having a vein that is little a bit swollen and is white colour. That vein in on the penis.
When I have an erection I pull back the foreskin and is very painful.

Welcome to the boards, Toshe.

There are a lot of possibilities with something like this, but since you're experiencing a lot of pain when you move your foreskin, this isn't something you want to try and use the internet for. As we make clear on the bottom of every page here, we -- nor anyone else online who can't examine you in person -- can't stand in for healthcare when it's needed, and this is one of those situations.

I'd make an appointment with your general doctor, and while you wait for that, I'd baby yourself and try not to do anything you can avoid that causes pain.