Sorry to hear about your problem, and this is especially sad given that you were in the middle of donating plasma. This is unfortunately not uncommon, and so you generally need to be observed for at least a short period of time to make sure that you can maintain your balance and be well. Now that you have hit your head, it is important to make sure that there are no long term problems that have resulted. For this reason, you should discuss this problem and any head trauma with your doctor
to make sure that you are safe and well. Headaches can stem from many different sources, and they could be a sign of a problem especially since they happened right after hitting your head so hard. In some cases, your doctor may feel that you need to have some testing, possibly including some imaging of your head, to make sure that there is nothing wrong. Your doctor will also be able to ask some other questions about your symptoms and your medical history that can help to know what else needs to be done. Finally, he or she can prescribe something if needed to help improve your symptoms. Please speak with your doctor.