Broken nose resulting in fever?

Hi,
My little brother broke his nose on wednesday and he's been running a high fever for three days now. (He's 6 yrs old). My parents have been to the hospital twice already, but nothing's been found, and his fever is still high. What could be the cause of this? He was slightly sick before he fractured his nose, so do you think that his fever is a result of his body struggling with the fracture as well as the virus?
What should we do next if the fever doesn't go away?