I have a painful lump in the right hand side of my scrotum since 4 days. it is near one of my testicles. is this a sign of testicular cancer?

Pain: That is not the usually presentation for cancer. More commonly is epidimal torsion. You should see a board certified urologist.

Possibly: A minority of testicular cancer patients present with acutely painful scrotal masses, but the symptoms you are describing warrant further investigation. Your doctor should perform a physical examination. Depending on his findings, he may want to order an ultrasound or some other tests.