For the last week and a half, I have had a sudden onset of Lower Back pain. It is not swollen or showing any signs of being externally bruised. I have not fallen and hit my back. It is not sore to touch, however when I lean down or sit down etc it feels moderately bruised. It feels ok when I am walking about. The pain is right in the centre of my back at close to base of my spine, just above my buttocks