PCP or Urology. A urologist will be ale to do a full exam of testicles, penis, and your prostate if appropriate based on your age and/or symptoms. A priamry care physician can also examine the male genital organs as well as do a full comprehensive physical as well. Your pcp will refer you to a urologist if its appropriate. You should see the physician you feel most comfortable doing the evaluation.
Ask, practice. Ask your doctor to instruct you in self examination of the scrotum/testes. It's important to know how to perform self-examination of the testicles for good health maintenance. Males in their younger years are prone to testicular cancer, and self examination is the best way to find treat and survive this condition. Check out lance armstrong.
Your personal doctor. A testicular exam can be performed by any licensed primary care doctor. If further testing is necessary it can also be directed by your personal physician.
Two options. Hello. Either see your internist first or go to a urologist. Good luck.