Hello and hope you are doing well.
If with movement you are getting pain it is likely to be an inflammation of the skin, subcutaneous tissue or the bone. This can happen with injury, repetitive activity or an infection of the skin. The other causes for the back pain could be infections/inflammations of the bowel, kidney disorders like pyeloneohritis, glomerulonephritis or renal colic. If it persists consult your doctor.
He will ask for blood tests, urine analysis, an x ray and an ultra sonogram of the abdomen. Sometimes he may ask for an Intravenous pyelogram and a CT scan. In the meantime take OTC Naproxen for pain relief and plenty of oral fluids.
Hope this helped and do keep us posted.
I would wait four days, and apply ice for 20 minutes than heat for 20 minutes (typical of what you should do for a pulled muscle. If it significantly gets better, my guess is you pulled a muscle in your back. If it doesn't improve see your doctor. And of course if you start to pee blood - go to the doctor ASAP.
It is was a kidney stone. Chances are you would be in a lot more pain.