Hello and welcome to HCM,
I have understood your problem and let me assure you that it is commonly seen and you have nothing to worry about.
Headache after a cavity filling can be due to both anesthesia
and also because sinusitis
. Furthermore, sinusitis is known to be aggravated by dental procedures.
You may start a course of antibiotics like amoxycillin-clavulanate
625 twice daily for five days along with pain killer like paracetamol
after food. Your doctor will know about these.
Also perform steam inhalation and do not take anything cold but take plenty of fluids preferably warm
If after about two weeks which is the usual time it lasts, if you are not feeling better then you must take a CT of the nose and sinuses
and get back to me or any ENT
Take care and get well soon
Dr Sriram Nathan