Dear friend, welcome to HCM.
Do not worry too much. cancer of testis does not present like this.
Do you have any fever, swelling, redness
along the testis or cord attached to it?
This looks like some tortion / pull of testicle with referred pain
which typically spreads to navel and up.
Simple step is to try scrotal support with a good underwear, seeing a surgeon to get evaluated for testicular abnormality (if any) and un ultrasound
of the scrotum
Do not weight-lift or strain too much.
That will give us a diagnosis and freedom from anxiety
I hope that will help.
Take care and keep me informed on your progress.