google lower back + stretching or exercises, find a routine that you think you will like

The one exercise I think helps me the most is laying on my back knees bent and pulling one knee to my chest. There are variations. It may not be as helpful to others. It is not the only one I do. My routine for the back takes about 15 min. But if I do my routine 4-5 days per week it keeps the pain under control.