My Father Was Getting A Drink While Standing & Got

My father was getting a drink while standing & got a little dizzy & fell backwards onto the kitchen floor hitting his head on the floor. It caused a goose egg on the back of his head. He feels ok other then his head hurts a little. He called my sister who lives 1/2 mile down the road from him. She stayed with him a couple hours. Should we just call him every couple hours? Could this be a lot more serious? He is 90 years old & lives by himself & is in reasonably good shape.