What Causes Lower Back Pain, Painful Hip And Bruised Knee After An Injury?

I slipped on Ice at work, and landed on my Left knee, only. when I did .....a surge ran up my spine, and neck, and the top of my head felt pressure. My knee is really bruised, and I had that looked at. xrayed. they said it was a bad contusion. My problem on is my lower back is feeling pressure and when I sit, I I have have pain over my left hip. who would I see about this, and would they take USPS, workmans comp. Does my problem sound like a possible severe problem.