Small kind of hard lump above Left Testicle im 13 help?

Im 13 and i found a lump attached to the top of my testical by a thin cord. It hurts when twisted and is the size of a small marble,maybe smaller. It is pretty much painless but sometimes there is a dull ache for around 1 minute then its normal again. It is attached to the left testical. It has been there for around 2 months and is the same size as it was when i first felt it. It isnt squishy but not even close to marble hardness. Serious answers only please. I already know to see a doctor, so dont say that. I wanna know what it is because im a bit freaked out