Now it is two weeks later and you hurt in the hip (buttocks area) and the pain might also be going down the back of the leg. And maybe that lower back is still gripping tight. What to do?
Did you ice the injury? What injury? I didn't fall? Yes, there was no impact. The muscles are still holding a muscle contraction. Check the muscles that hurt. Are they hot or cold. Use the back of your hand to check. Add heat if they are cold and ice if they are hot. Continue with the ice and heat and ice. This will increase the blood flow into the muscles allowing the muscles to release the tension.
Next do stretches for the lower back, hip and legs. This picture shows a demonstration of a hip stretch. Do this stretch sitting in any chair. The leg of the hip that is in a bit of pain, place that ankle over the opposite knee. With a straight back, lean forward, flexing at the hip. Do not curve the lower back. Feel the stretch in the hip.
You can view a good explanation and demonstration of the sitting stretch for the piriformis muscle, for back pain and sciatica nerve pain with the Dr. Steven Hoffman on this youtube
This youtube video by Oscar Sanchez demonstrates a way to stretch and massage the hip muscles using a ball (use a ball with a bit of bounce like a tennis ball) to release the tight piriformis and gluteal muscles that is pinching the sciatic nerve. This youtube video by Oscar Sanchez demonstrates five floor stretches for the lower back.