Since how long are you having these symptoms ?
Is there any associated acid reflux ?
Any associated burning while urination ?
Is the pain located on the back side ? Does this radiate to the lower abdomen ?
Sludge / stone in the kidney can cause pain in the area you describe .Also since you also have related urinary symptoms as well a urine examination and an Ultrasound examination should be considered for further evaluation in your case .
Also there can be associated hydronephrosis ( It is distention and dilation of the renal pelvis, usually caused by obstruction of the free flow of urine from the kidney.) which can also cause dull pain .
SInce there is no associated history of muscle strain , excercise or trauma further evaluation to rule out renal cause of pain should be considered especially since there is associated urinary symptoms .