or Orchitis) or inflammation, testicular torsion(most common in young men between 10 and 20 years old), excessive bicycle riding, hernia or kidney or ureteric stones.
The final diagnosis can only be made after a thorough physical examination including examination of the abdomen, scrotum, testicles and rectum.Pls consult a urologist for that.
Lab investigations like complete blood examination, urine examination, ultrasound lower abdomen and sometimes a urethral swab will help in diagnosis. Treatment will be started thereafter.Hernias are to be dealt surgically.
I hope that helps. Please do keep me posted on how you are doing or if you have any additional doubts.Warm regards.