I think the pain is telling you you need to see a Doctor and do not delay. Not to frighten you or mislead you, but testicle cancer is on the rise. I hope it is something minor, but let your mind rest by seeking professional medical advice and it is a slim to non chance they will want to advise you over the telephone. Best wishes
The pain in the testicles can be due to orchitis that is inflammation of membrane of testes. It can also be due to hernia. The other reason can be varicocele. The differential diagnosis is required for proper diagnosis and its treatment. Visit a doctor.