What damage could be caused from being hit in the side of the head?

This sounds really retarded but I was outside watering my lawn today and I was yanking the hose across my yard. Well I couldn't see the end and it was closer then I knew. Then I yanked it REALLY hard, well the nozzel ended up hitting me in the head real hard! It hit on the left side a little less than an inch above my ear. This happened at around 2ish pm today. Its 1 am now and it's really sore when I touch it and I have a little headache, should I be worried? And could it have caused any damage? What should I do?