Endoscopic surgery 5 days ago. i have dull sinus headache and significant pain behind my left eye. should i call doctor?

Yes: What part of your anatomy was scoped? But discuss with physician. Could be medicine response or reaction to procedure.

Yes: This should be checked by a professional to make certain that nothing serious is in progress. Good luck.

Yes- call: If you are having significant pain after surgery, always call your surgeon. Generally sinus surgery can cause some mild headache but i wouldn't expect severe pain.