I Fell On My Back On The Stairs A Week

I fell on my back on the stairs a week ago and up until last night I was improving nicely. After a real good night sleep I woke up and when I tried to get up I wad incapacity with extreme pain worse then the day it happened. I made it through today but still extremely sore. To make matters worse I an battling a cough. Guess my question is how could a good nights sleep hurt me?