I fell straight on my knee, but the pressure of the fall hit my hip joint, what do I do?

Your hip joint is very precious, you need to take care of it. I would go to your doctor and find out what he thinks is the best alternative for you. Two years ago, I fell forwards and landed on both of my knees, I hurt my hip and ignored it. A year ago, I couldn't get up to save my life. You can severly damage your hip for life if you put too much pressure when you shouldn't. Diseases such as cocyndia and complex regional pain syndrome (I now have.) can both be caused by a fall. Get yourself checked out as soon as possible. Even if it doesn't seem like that bad of a problem, it can be in the long run.