If the back of your hip and your low back are feeling really stiff and achy, there's an easy stretch that you can do while you're lying down.
When you're lying on your back, cross your ankle over your knee, grab the knee with the opposite hand and pull the knee towards its opposite shoulder. You should feel this stretch on the back of your hip.
There's a little modification that can make this stretch so much more effective.
If you position the foot that's on the bed a little farther towards the outside you're going to feel the stretch so much better in the hip. Hold the stretch for 30 seconds and do it four times in a row.