During my self defense class when falling back i hit the back of my head hard to the point where i was a bit woozy.head hurts a little.should i sleep?

Yes you can sleep: But alert your family or company at home to keep an eye on you at night. It is unlikely that sleeping is going to cause any problems. If your have a problem in the head, it will keep you awake or it will wake you up from sleep. Increasing headache is a symptom that would come on if there is any bleeding inside your head which is all we have to worry about.

ER: I am suggesting to visit the er for further investigation and ct. Better safe then sorry.