Something like ulcer on my testicles, it stings on the touch

Hey there it's hard to say without seeing it. You say you are a virgin but have you ever had oral sex either?   Do you shave your scrotum? Did anyhing leak out of it?

Look up the symptoms of testicular cancer and of the different STDs and of normal skin infections, acne, and skin boils. See what is most like what you have. Those are the things that most often make problems like that on a man's balls. The biggest question you need to answer is whether this problem is on the outer skin of your scrotum (ball sack) or deep inside your ball sack and on the actual ball itself. If you can see it, then its on the skin of your sack and will move around with the skin and not deep inside on your ball. Your balls can both move around inside your sack and move separate from the sack skin.