What Causes A Black Eyes 3 Days After An Injury To Forehead?

I fell backwards down a flight of approximately 17 stairs. I did hit my forehead on my hair line and had a bump for a few days. Three days later I started developing a black eye which is literally now black and is crossing over to my other eye. I have no eye pain in movement, no headaches, no blurred vision. I never lost consciousness. I am just concerned that the brusing is getting much worse. Is this normal?