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
*Tab Flexon (1 tablet after lunch and 1 tablet after dinner for 7 days) (if you are not allergic to it)
*Tab Pantakind (1 tablet before breakfast in the morning for 7 days)
*Tab Gabaneuron (300mg) (1 tablet at 7pm for 10 days)
*Do Bhujangasana (start with 5 counts per day and slowly increase the number of counts till you reach 40 counts per day) (this is very important!)
*Avoid sitting on a chair/stool for more than 15 minutes at a stretch. After 15 minutes, get up for 1 minute and then sit again. This is extremely important!!
*Whenever you sit on a stool/chair, make sure you sit ahead on the edge of the stool/chair. This way you will automatically sit straight. If you go back to take back support, after a while, you will bend your spine backward. This will increase your back problem.
*Avoid sitting on soft sofas.
*Avoid riding bike/car as much as possible
*Avoid bending forward with your knees straight. Bend your knees and then bend forward.
Next Steps
Follow the above steps and do let me know after 1 week if you have less pain.