There are a few things that could be going on. My first thought is post traumatic headache. Here is a link to a thread from a while back:
I would recommend reading through the link in the thread to the review article. If you do go the PT route as a supplement to meds, finding someone who specializes in trigger point therapy is a definite plus.
You would be surprised by how little force it takes to set off an episode in some individuals (especially those that are headache and migraine prone).
Bruxism? Yes, it can cause headache and is a very common trigger for headache and/or migraine. In the majority of cases, a specialized hard mouthguard made by your dentist solves the problem (along with eliminating common bruxism triggers e.g. smoking, caffeine, minimizing stress, etc. ).
Unless you are clenching or grinding throughout the day though, it would seem weird that the pain would be constant and would get worse throughout the day (b/c of the bruxism). The timing of the headache and fall is too coincidental. I think the most likely scenario is post traumatic headache alone is the root of your issues, or post traumatic headache in combination with bruxism is tipping the scales to cause this episode.
Was the CT of just the head or of the head and neck? Did the chiro say anything, like... oh, such and such feels out of place?
Best of luck!