hi, i am a active 25 year old male, about 10 years ago i found a small hard lump on the back of my left testicle, i really don't have any discomfort with it, but i have had in the past, it doesnt really worry me, but i though that i would get some advise, ive had it there for about 10 years and it hasnt gained in size and i get no more discomfort it... what could it be?