Pain in lower right side of back, looks a bit swollen there. Urine culture is clean with no sign of infection?

Back pain. It could be due to some kind of trauma, probably went unnoticed by you. Back pain is very common, but it should not be accompanied by swelling. You can observe for some time, it may go away with posture change, exercise, message or pain medication. If pain persists with swelling then see your doctor for x-ray studies.