Hard lump under left testicle

I might have noticed this about a year or two ago but at the time I shrugged it off as "part of the system" down there. I recently discovered it again after feeling around down there for a while (it's difficult to narrow down its exact location) and now I am kind of concerned about it. Here's what I know:

1) It's a hard lump about the size of a pea under my left testicle.

2) It doesn't seem to be attached to the testicle itself, but I'm pretty sure it's attached to part of the lower (tail or duct) epididymis, or perhaps something else other than the testicle itself. For the most part it free-flows independently of everything else, but it is attached to something!

3) I can usually find it by standing up straight, reaching my fingers under my left testicle and placing my thumb at the top front of it and my fingers at the top back of it and slightly squeezing it and gradually pulling my thumb and fingers down until I get to the bottom of it. Just as the bottom of my testicle slides away from my thumb and fingers I can feel the lump, which I can move around freely without really moving the testicle.

4) If I lift my left testicle up so that the bottom is pointing at my face, the lump is sometimes visible through the scrotum skin and if I move the lump too much it "falls" down the side of the testicle and stops being visible. When the lump is visible through the skin, it almost looks white.

I am 25.

Does this sound like testicular cancer? I am hesitant to seeing a doctor but I am going to push myself to get this checked out in the next couple of days.