Do you mean your abdomen or your back?
ANy blood in the urine?
Does it burn when you urinate?
You certainly could have an infection in the urine. Another consideration is a kidney stone. Usually you will have blood in the urine from a kidney stone.
It is important for you to have a urinalysis and an exam done to determine which one it is so correct treatment can be started.
Keep drinking plenty of fluids though until you can be seen.