At your age, improper posture and prolonged sitting can cause such issues.
If you have severe pain, try the following:
*Lie down in the bed on one side (left/right...whichever is comfortable for you) , fold your knees and keep a pillow in between both the knees. Lie down in this position for 48 hours. Get up only for using the toilet and for having food. Do not sit, stand or walk.
*Apply ice 5-6 times a day over the back. Don't apply any balm/gel/spray/oil.
*Tab Ace Proxyvon 1 tablet after lunch and 1 tablet after dinner for 5 days (if you are not allergic to it)
Next Steps
After 48 hours, let me know if you have less pain. If the pain reduces, we can start our daily activities with certain precautions that I will tell you. If the pain does not reduce after taking rest for 2 days, then see an Orthopaedic surgeon or get admitted to a hospital.