Pain and numbness in left leg.

Patient: Can a pinched nerve cause numbness in the shin?

Symptoms: About 3 weeks ago. I bent to tie a shoe and did something to my back. I was treating it with rest, stretching etc and it was getting better. Two days ago, my lower back and left leg became so painful I have been flat on my back ever since. My back no longer hurts but when I stand or sit I get sharp pain in my front thigh, down the side of my thigh, and down my shin which is now getting numb.
Can you give me some idea of what is going on?