Sacroiliitis. Likely inflammation of the sacroiliac joint. This a joint between the sacrum and the ilium. The joints are located bilaterally where the small dimples in the low back are located. Pain in this joint is made worse by rising from a seated position, rolling onto the affected side while in bed, and taking a step up on the affected side. Apply ice at night in addition to the diclofenac.
Nerve impingement? can be caused by being sandwiched between two spinal bones, pressed by a bulging disc. It can cause muscle spasm and back pain. Prevention treatment is always recommended. This condition must be professionally managed. See interventional pain management specialist for definitive diagnosis and management.