It is always important to listen to your body and the signals it give you. However, this movement is one of the safest ones for low back tightness and pain.
Not only does it feel great in most instances, but it's a wonderful way to restore flexibility in your low back muscles. The knees-to-chest stretch may help reduce stiffness associated with spinal arthritis and/or spinal stenosis.
However, common mistake of people is that they aggressively perform the double knees to chest, which can lead to low back irritation and pain. It is recommended for you to perform lumbar flexion in a cautious manner and with 95% of people, they would benefit from lumbar extension compared to lumbar flexion
If you are unsure whether a knees-to-chest stretch is safe given your particular back condition, speak with your healthcare provider before trying it.