I have an old saying.."back pain in the absence of fever is never from the kidney, it's from the back". The main exception to this is kidney stone and the red flag for kidney stone is blood in the urine. Therefore, I believe you need to be worked up for kidney stone disease. You need to have a renal ultrasound exam to be sure there is no obstruction to the flow of urine then probably a CT urogram.
My recommendation is for you to see a urologist and if for some reason, no stone is found, then a nephrologist because if there is no stone, the blood still needs to be evaluated and he/she would be best qualified to do that. I bet you have a stone though.
Thanks for your question and I hope this helps. Please feel free to follow up.