I have dark veins on my left scrotum and after activities like playing football it hurts so much that i can't walk, is it varicocele?

Not usual.: It's worth a look by a doctor or even a urologist. Varicoceles are usually felt through the skin of the scrotum as a soft mass on the testicle, not so much seen in the scrotal skin itself. The pain is a concern. Best have it looked at before your next strenuous exercise.

Scrotal veins.: It is not uncommon for men to have veins on the scrotal skin and these can become irritated from pressure or sweating. These veins can be light or dark and tend to darken with age. A varicocele is within the scrotum and not on the outside of the scrotum.