lots of reasons for that, please get assessed by a urologist,,
dr R U
What is your age? Common reason for a low grade dragging pain is varicocele (engorgement of veins). The best approach will be not to wait on it but to see an appropriate doctor, usually urologist for adults and a paediatric surgeon for under 18 years.
What type of pain you feel? Any injury you had?
Anything hit up in your testicles???