Acute Back pain not radiating to legs requires rest, ice back application, Lumbosacral belt application, some analgesics and muscle relaxant. But this pain has come due to improper posture and activities. For long term prevention of this pain you need to visit physiotherapist after this pain goes and learn exercises which should be done everyday for few months to prevent it coming back

Dear one Dr Archana and Dr Madhur have already given a satisfactory answer to your query, I would like to add, to take rest and analgesics, and see if it resolves, MRI has no indication in pain of 2 days without redflag signs.

Give complete rest to back. Try to lie down as much as possible. Apply pain balm or spray and hot water bag. Take care.

Take some skeletal muscle relaxant, and some hot fomentation. If pain doesn’t improve, get an MRI