Thanks for posting your query.
From description it seems soft tissue injury
or ligamentous injury over your lower back.
You need bed rest
for few days which helps in healing.
I advice you-
• Lie on a hard bed.
• Anti -inflammatory drug like ibuprofen
to reduce pain and inflammation.
• Avoid forward bending.
• Avoid strenuous activity & lifting heavy weights.
• Apply diclofenac
gel on the affected area.
Wishing you good health
Dr Saurabh Gupta