left testical hurts! need advice!

ok im 14 and im not sure if im goin through puberty. i think i may be just starting to. but today in school my left testicle started hurting alot. i was actually doing some research on testicle a few weeks ago though because i noticed a lump.(i think) its not attached to my testicle but its about the size of a dime ( oval shaped ) and is black. there is also like a black vein on the top of my testical (left) it could be something that is supposed to be there but i have no idea ive just realized it recently. for all i know i could have just noticed it because it got larger because i may be starting puberty. and i was just at the doctor a few days ago and it was not for this reason but he did a partial testicle exam? didnt tell me anything was wrong but he wasnt looking for anything like that. but i want to know if this pain is something serious or if it is just something pubicly related. please leave your thoughts