I have a very bad pain in my leftside hip, what is causing it?

I injured my hip a few weeks ago, if that helps at all, by my friend accidentally falling on it. It has been fine ever since except for when it first happened it hurt to take long strides. Less than a weeks ago I woke up with my hip pain that severely discomforted me with sharp pains coming from the area I injured it. It is coming from the front left area of the hip. I found a positions where the hip wasn't being hurt (laying on my right side with my legs together and bent slightly) and was fine the next day. I thought it was a random occurrence until it happened again tonight. I guess both days I was fairly active, more so than I usually am, I suppose that is important to. Besides visiting a physician, what is the best idea or advice for what is wrong and what I can do about it?