What Causes Numbness From Knee To Thigh After An Injury?

I fell over a gate at the bottom of the stairs a couple hours ago. I had immediate pain in my foot and twisted my body as I fell, within 30 minutes of the fall my leg and foot mainly inner lower part of my leg upto the knee has gone completly numb. It does seem to be migrating upward to my outer thigh now. Is there a need for concern?