What Causes Spinning Sensation After Hitting Head By Mistake?

I slipped on ice fell backward and the back of my head hit concrete pavement .I was checked by City paramedics and my vitals were OK.I also strained my left knee during the fall. I have taken 3 acetaminophen w/codein and iced the back of my head and knee.i recently soaked in my hot tub spa and when I dipped my head backward under water experienced a significant spinning sensation similar to vertigo.My M D will see me in the morning and arrange for a Ct scan. Did I do the right things?