If the Rct is complete and properly done there should not be any pain due to it. However pain on pressure could be there if tooth is not reduced . The pain in eye and headache could be due to different reasons such as related to sinus etc . Do tell your dentist about it and get it cross checked with X-ray for any associated infection. .

Visit ur dentist for assessment , but ur symptoms are pointing towards sinusitis.

After completing RCT,  there should not be any pain in that region,  Consult the dentist again,  Tell him  your problem,  He may take Xray to reconfirm the treatment. Eye n Headache may not be connected to the tooth.  If root canal is ok you can consider other reasons for headache n eye pain. 

If your RCT has been done properly and completed fully there should no longer be any pain in that region more than a week. Eye and head pain after a lateral rct is extremely rare. One possibility is an irritation of your sinus which may be causing pain. It may also be unrelated to your teeth. Please revisit the dentist to make sure that tooth has been relieved from bite pressure. And take a confirmatory xray to make sure the rct was properly done. If all looks ok then consider other reasons for headache, or else repeating the rct should be undertaken.

Hello..Generally after RCT pain might be there for 3-4 days.Kindly visit nearby dentist to evaluate clinically and radiographically to determine whether RCT is done properly or not.

Hello, As a Root canal specialist,generally there should not be any pain post treatment. In a few cases however pain/discomfort can last for about 4-5 days after RCT. We need to take another x-ray and check if the RCT is done properly.Regards,Dental Arts,jayanagar,Bangalore

Get  radiograph of that tooth .There are so many reasons for RC treated tooth.May be filling is beyond apex.

Get it checked . may be due to problem in any other tooth if rct is fine

Ideally after 20 days one should not have any pain in treated tooth, but we normally wait for 7 to max 10 days in few cases for pain to subside, in your case you already have 20 days crossed, so you should consult your dentist to evaluate whether its tooth related infection or any sinus related issue, later he may advice you for few xrays, go for it, he will surely guide you what to go further in it, still not satisfied go and visit an endodontist.