Hello ,I am Dr.Sadaf , i have gone through your query and it appears you have incurred a muscle spasm or muscle pull in simpler terms while bending. Its something which can resolve if you massage your lower back or have warm compresses using water bag. Yes ,i would definitely advice to walk as a pain relief measure after your pain has subsided a bit. You can apply local pain relieving ointments if it helps. Sleeping can all the more cause more back pain in the long run. If you feel any tingling or numbness in your feet or any bowel or bladder incontinence please have yourself assessed in any nearby clinic. Hope that serves your concern.