So there is a line on the scrotum called the scrotal raphe. It's down the middle of it, and it separates the left and right sides.
https://en.wikipedia.org/wiki/Scrotal_septum#/media/File:Figure_28_01_02.JPG has a pretty decent image of it.
Is that what you are feeling, or are you feeling a swollen vein?
Any symptom that comes and goes is not likely to be an STD symptom. Tingling is also likely to be more an anxiety symptom, and not an STD symptom.
However, if you're concerned, you can easily go to your doctor, an STD clinic, or go online and get tested. There's no reason to sit and worry about it when testing is so easy - just literally go pee in a cup.
Certainly, if your thoughts are going towards cancer, go get it checked. If you haven't ever had your testicles checked out, get that done and find out if things are okay.