What Causes Severe Pain In The Hip?

I am an 18 year old female experiencing moderate to severe pain in my left hip. It started after a long uncomfortable plane ride about two weeks ago. It doesn't seem muscle related, but instead feels like bone grinding against bone. The pain subdued about two days ago but has come back today. I have difficulty rotating my hip, and end up limping when i walk as to avoid putting pressure on my left hip. Any ideas to what may have caused this, or what it is?