At your age, low backache is common due to improper posture, prolonged sitting and wrong ways of bending forward.
Try the following:
*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 (40mg) (1 tablet before breakfast in the morning for 7 days)
*Tab Gabaneuron (300mg) (1 tablet at 7pm for 10 days) (this may cause some sleepiness for the first couple of days)
*Lie down on your stomach, keep both your palms beside your shoulders, press your palms on the bed so as to lift your upper body up from the bed, then bring the upper body back down towards the bed (Bhujangasana). Repeat this for 40 counts.
*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.
*Sit erect. This can be achieved by sitting on the edge of the stool or chair. Don't go back towards the back support!
*While bending forward, make sure to bend your knees. Don't bend forward with your knees straight!
*Avoid sitting on soft sofas. Sit on hard stools/chairs.
*Avoid riding bike/car for a few days until your pain subsides.
Next Steps
Do let me know after one week if your pain has subsided.