How are you? Pain caused by the kidneys is typically felt in the flank area, which is in the back, just at the lower edge of the ribs on either side of the spine. Pain caused by the kidneys tends to be sharp, severe and occur in waves.
It is rare for the kidneys to cause dull, aching pain. People sometimes equate back pain with kidney pain, but dull aching pain in the back , especially the lower back or the middle of the back is usually due to muscles, ligaments, or even vertebrae and disks in the spinal column. Musculoskeletal pain typically gets worse with movement, and is relieved by heat or massage.
The causes of kidney pain could be stones, infection, tumors, polycystic kidney disease and urinary tract obstruction. As you mentioned that you don't suffer from all these, and the kind of pain you mentioned does not refer to the kidney pain.
So, I would advise you to get an ultrasound with X-rays of spine done and visit an orthopaedician.