It can be due to any fall or hit by something, then its not a big issue, can be treated very easily with Physiotherapy.
Is there any history of pain in the back or pain travelling down the thigh?
Pain in coughing /sneezing?
Do u tilt while walking/sitting?... It can be die to any nerve compression as in case of disc bulge.
Next Steps
Consult a physiotherapist.. Ultrasonic therapy +IFT +Heating therapy +some strengthening exercises will be helpful for sure.
Health Tips
At home.. Rest +hot water fomentation +pain killer gel +no long sitting /standing /travelling /walking /driving +no cold exposure +no manual exertions +no stair climbing+ Sit tall(correct posture)