dull ache around the kidney area.

[Costanza]

Always in the same place? Unlikely to be an infection if it recurs and you don't have fever. Stones are a possibility, but the pain from kidney stones is rarely described as a dull ache -- more along the lines of "somebody cut this [censored]ing thing out of me before I go insane" kind of pain.

Lots of other possibilities. Most are completely benign but worth investigating, especially if you're in the 35+ crowd and haven't had a recent exam. Go see your doctor.