Fell Down And Hits The Back Of Head. Started Vomiting. Is This Serious?
I am sorry to hear that the baby hit the back of the head. IF the baby was previously healthy and the vomiting started right after the hit then this is somewhat concerning. A concussion can cause multiple symptoms in a baby, but the first one usually is vomiting. Monitor and make sure he/she does not become drowsy or unarousable. My best advice would be to have the baby checked out by a pediatrician just to be safe, since babies are very fragile and can't communicate if they is something potentially serious going on.
I don't mean to alarm you, as most of the time nothing serious happens, and everything resolves by itself after a few minutes, but the safest thing is to have him checked out by a professional.
Hope that helps, let me know if you have any further questions