I think the advice to see the doctor first is the best route to go on this one. Having said that, I have a very large road-rash scar on my left leg that required some skin-grafting and I have a somewhat large burn scar on my ankle from a motorcycle muffler that lay across my ankle and just burned a large groove into it until someone came and lifted the bike off. The ankle burn is partly covered by my sock when I ride, so no worries. The road-rash I have to be careful with. It does get sun-burnt and has split before - which is very painful. I cover it with sun-screen, and if I'm doing a long ride (100 miles) will use a zinc cream on it. After that I always have to rub some type of moisteurizing cream into it (I like aloe-based stuff) or it can dry out and crack.

Please, go see your doctor. Some creams can cause skin reactions.