could just be ur system shuttind down, if the pain doesnt go away you could have a bacterial infection... i went to the doctors cuz the same thing happened to me and i could barely walk from the pain, was diagnosed with epididymitis... its just an infection, meds took it away in 3 days, funny thing though, the doctor told me to go home and wack off cuz sperm is a cleanser, so it would clean my system out down there if i masterbated... kinda funny, but it worked, and the meds helped