I'm 18 with a worrying testicular problem?

I am almost 18 years old, and I am very worried about a dark blue,black blotch which is under my scrotal skin but ontop of my testicle, it isn't completely flat, it is raised by about a quarter of an inch and the pain has increased from occasionally to frequently, I went to my doctor, he said it may be an epididmal cyst however he told me to come back in a month if it changes or hurts anymore which it does, I do not believe it is testicular torsion as I am not really producing an less semen. The splotch is only visible if i sit at an obtuse angle and sometime it even looks like a vein, the splotch is not on the other side of my genital, it is at the top of my testicle located slighty to the right, under my penis but attached to the testicle, I am going back tommorow but I was curious as to whether anybody could give me any ideas of what it could be.