At your age, improper posture and prolonged sitting can cause such issues. If you are not careful, you may develop slipped disc!
Try the following:
*Apply hot water bag (10 minutes twice a day)
*After applying hot water bag, apply Nobel Gel
*Do Bhujangasana (start with 5 counts and slowly increase the counts until you reach 40 counts per day)
*Avoid sitting on a chair for more than 15 minutes at a time. After every 15 minutes, get up for 1 minute and then sit again. This is very very important!
*Whenever you sit on a chair/stool, sit ahead on the edge of the chair. Don't sit back to take back support! If you go back, after a while you will bend you spine. If you sit in front on the edge of the chair, you will automatically sit straight.
*Avoid bending forward with your knees straight. Fold your knees and then bend forward.
*Avoid sitting on soft sofas. Sit on hard surfaces.
*Avoid riding bike/car as much as possible.
Next Steps
Try the above steps and let me know if you have pain relief after 1 week.