I am 44 year old male, my dad had prostate cancer.  i found a lump on the outer sac of my right testicle with pain.  is this common or shld I worry.?

See MD. It could be an infection/inflamation like epididymitis, orchitis or testicular tosion, hernia, etc. You should see your md and have proper evaluation that will include an ultrasound to your testicle. Most likely, this has nothing to do with your prostate cancer history in your father.
Testicular lump. You may have a sebaceous cyst or infection on the scrotum. This sounds completely unrelated to prostate cancer. Go see your doctor.
Get it checked. The prostrate is not in scrotum this likely a spermatocoel benign not cancer you can't feel prostate through rectum no self exam available.
Not prostate ca. Prostate cancer develops inside and locally around the prostate. The prostate is located on the back of the bladder and in front of the rectum. That is why a prostate exam is done by rectal exam or rectal ultrasound which allows easy palliation and visualization of the gland. The testicles are not anatomically very close. A testicular lump needs md eval to see if its solid or cystic. B9 or malig.
Get exam. Any new finding noted on self exam should be reported to your physician and examination should be performed in the office. This has no relation to your risk of prostate cancer however.