I have a dark vain on my sack that is really dark. i haven't noticed it till about 9months ago. is this something i should get checked out?

Vein on the scrotum: Some veins get to be more prominent anywhere in the body including the scrotum. If it is a single one, it may be ok. Sometimes men present with a condition called varicocele where extensive venous net is seen through the skin, usually involving one testicle. In that condition, there is more than just one vein visible and the condition is compared to a bag of worms.