My 9 months old baby just had a bang on the back of her head against the floor. She was playing on the floor when she lay backwards and knock the back of her head on the marble flooring. Anything to take note?

Check for injury. Monitor for vomit or fever or loss in appetite or always very very sleepy or over cranky or not active. If sleeps to long try to make sure is responsive by tapping or calling the name. The first 24-48 hours is vital. Any signs please go to the hospital.