Your back muscles are into spasm and also disc of your spine may b inflamed.
Next Steps
Apply cold pack for low back. Apply volini or voveran gel. Ly down on your stomach for 2 mins. Then ly down on your stomach and go up on your elbows like you watch tv when you are lying down on your stomach. Try these exercises. There very simple.
Health Tips
Avoid bending forward
Avoid sitting on floor
Avoid lifting weights
Show to orthopedic and then consult physiotherapist for further management