Quite often the cause of back pain is musculoskeletal. You may have slept awkwardly, or incurred some other gradual physical trauma. Topical ice would help control the stifness/spasms. You also could apply topical pain cream such as Aspercreme. If there are no other symptoms, the it s just a matter of rest and pain control until it heals and resolves. But if over the counter pain meds aren t cutting it, then you may need to see your doctor to get something stronger, and/or a muscle relaxant. Another quick option is chiropractic.