I have a pain in my back on the left side mid way down. It started around 8pm last night. I took a muscle relaxer, and now at 12:46 noon it still hurt?

Back pain. Could be musculoskeletal, it may take several day to get better. A kidney stone could produce that type of pain. If not getting better seek help.
Heat, ibuprofen . Hi! if it started spontaneously it is probably a muscle spasm. Try a heating pad for 15 min every 4 hrs, and take an anti-inflammatory med like Ibuprofen or naproxen. A hot bath or jacuzzi may also help. Warning signs for something more concerning include fever, pain radiating down your leg, shortness of breath, foul-smelling urine. Good luck!