Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Without the ability to examine you and obtain a history, I can not tell you what the exact cause of your symptoms is. However I will try to provide you with some useful information.
In the setting of trauma, such as the fall you experienced, a headache could simply be due to muscle strain or bruising. However, it is important, especially in people your age group, to rule out small bleeds, most commonly what is called a subdural hematoma, or a collection of blood under the layer of tissue that surrounds the brain. A contusion, or a brain bruise, can also occur. This is best assessed with a CT scan of the brain.
A concerning cause of neck pain associated with headache is a dissection: a small tear in the blood vessels that travel up the neck to the brain. This can occur spontaneously in people with certain conditions that affect the blood vessels, after neck trauma, or after chiropractic manipulation of the neck. The pain is often but not always associated with some sort of neurologic deficit as a dissection can often lead to a stroke.
I do strongly recommend that you see your internist for further evaluation, just to be on the safe side, he/she can examine you and order appropriate testing as indicated.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.
I am not a neurologist but I am an OT - any time you have a significant fall and do as much damage as you describe, its worth checking in with your internist. If you took a really hard hit to your head then you can have a concussion or worse and its not always obvious initially.
Also the reason you fell, is as important to know,( esp when you are a senior), as any injury you may or may not have sustained due to the fall.
Check in with your Dr regarding your ongoing issues and I hope you feel better soon.