I've not had a vasectomy before but I've had testicular cancer and if there is a lump in your testicles, you need to have it checked right away. A Urologist will send you to have an ultrasound of your testicles which will shed a big light on this - also having blood test for tumor markers (AFP & HCG) may be ordered as well. Let me know if I can be of further assistance once you have a diagnosis..good luck!