I fell 2 days ago on my knee and scraped it very badly. It still hasn't scabbed over completely. I am keeping neosporin and a bandaid on it. A few hours after I fell, I noticed a red ring form around the large scrape. It is swollen and hard. It hurts to touch anywhere near the spot and the red ring is continuing to expand across the rest of the knee. I can barely walk on it because it hurts so badly. I cannot completely bend my leg or lay it straight. What should l do? What's causing the swelling?