Why do i get an ear ache and headache after having a filling?

Referred pain: It's likely that you are having referred pain- the pain from the work you had done is referred to the ear on that side- especially true if it's teeth on the upper jaw. If the pain is in the TMJ ( the joint where your jaw meets your face) it could be from opening your mouth for long periods of time and maybe you don't need to open it as wide as you do.