I'm having pain in my front tooth after having a root canal

I'm having pain in a front tooth after having a root canal about a year ago. Around two weeks ago I went back to my dentist because of having slight pain in that tooth. My dentist said that this pain was being caused due to that tooth grinding against a bottom tooth and there was pressure. So he filed down the tooth that I was having pain in. Three days later when I woke up a whole corner of my tooth had broken off. From that morning I have been having severe pain in that tooth and it is throbbing and extremely sensitive. So I called my dentist and made an appointment but due to my job was unable to get to the dentist until the end of the week. Due to the pain that I'm having I requested that my dentist call in a prescription for the pain. My dentist then told me he couldn't do that because it is impossible to have that kind of pain after having a root canal done and told me to just come in on friday and would x-ray the tooth. Is it possible to have pain after having a root canal?  

[feelinglost824]

Did your dentist take an xray to determine that there was no infection at the apex of the tooth?  

[JLW1105]

Well my appointment isn't until friday , but on the phone today he said that it is impossible to have pain after having a root canal because the nerve is dead. But if the x-ray on friday shows no infection is it possible to have pain in this tooth, and also is it possible that the reason it broke is because of the dentist filing it down?