Problem with pimple on testicles?

i had what looked like a pimple on my testicles, so i tried to pop it but i did not work. i had it for 4 days already. it might also have been something else, i shave down there so it could have been something brought on by that. i am sexually active but i do not think its anything related to that. when i popped it with a safety pin (i Sterilized it) it was a clear liquid mixed with blood. it was hard and kind of hurt so that was my reason for popping it. can anyone tell me what it was?