Straightening of lumbar spine may be due to muscular spasm in lumbar region. There is a possibility of prolapse Intervertebral disc which might be causing the problem.
It would be better to get MRI of Lumbosacral spine to confirm the diagnosis.
Next Steps
You should start hot fomentation, take analgesic with muscle relaxant tablet, take
calcium and
vitamin d supplement. Physiotherapy including Local US, SWD will help you in relieving the pain. Use Lumbosacral belt for support.
Health Tips
Avoid heavy work, avoid sitting down, avoid Indian toilet, avoid forward bending, avoid stair climbing and descending..