Thank you very much for the useful information Michael.
I am glad that you already had a CT scan done, which has ruled out any serious possibility like a circulation issue to the brain or haemorrhage or a mass lesion.
This is most likely a result of high blood pressure (if your readings were high when this started) or simply a tension headache (that occurs due to physical or mental stress, sleep issues etc) because of spasm of muscles in the scalp.
Since the pain severity is minimal, and there are absolutely no neurological symptoms (and with a normal CT scan), i would not consider this very much concerning or serious at all.
Continue to use Advil alone or in combination with Tylenol for another 48 hours.
Have adequate sleep.
Little bit exercise.
All will help and most likely this will settle down soon.
My goal is to provide you with Excellent Service - if satisfied with the response, Please do not forget to Rate my service as this is the only way i get credit for my time and expertise on your question.
If you feel you have gotten anything less, please reply back, I am happy to address follow-up questions.