playing the odds...its low back pain and will pass.
or maybe you have a giant tumor in there (or a worm) eating its way thru your spinal cord. I dunno.
as kilgore states....more typical is extreme pain, intermittent, unilateral, +/- pissing blood.
The good thing is either way you'll soon find out. If stone then "it will present itself over time".
Chances are its just back pain that will spontaneously resolve and there's no satisfactory reason for it coming on or leaving.
or . it could be a giant fucking tumor eroding ....