What Is The Treatment For Abrasion On The Leg?

I have an abrasion on my leg just below the knee which I had attained 5 days ago by falling in a drain. At the time I had went to the hospital and they said that it was only a minor abrasion even though I had some difficulty straightening my leg; and they had given me some pills to prevent it from being infected. I finished taking these pills 2 days ago and after I had finished them it seemed like my leg was getting better. However these last two days it seemed to have gotten even worse than before. The area around the abrasion, which had already turned into a scab, has been swelling up and there is a small area which is severely discolored. Now, my whole leg has turned yellowish and the swelling keeps increasing. Now I cannot straighten my leg at all due to the severe pain. Help?