What could it be?

Patient: Hello, i didn’t know which section to put this inI was wandering if you could give me some advice.About just under a month ago i fell down my stairs but didnt break anything i just badly bruised the top of my left leg and i had some swelling too.And now whenever i am in bed or lying or sittting and keep it in the same place for a long time and try to move,walk orturn over in bed i get a big sharp pain go from the top of my leg down as if it was muscle it is sometimes enough that i loose felling in my foot and sometimes i have to sit back down it is that painful, but then after abouts 10 – 15 mins of using my leg mainly walking it is kind of back to norm.what could it be, could it be muscle, or something else?thank you for your time