Small hole in filling portion of root canal next to the post. Is this normal?

Yesterday I had a temporary crown which covered my root canal, it came off while I was eating and exposed my tooth and gum area which my dentist had shaved down. There was a small hole in the filling portion of my root canal (in the center of my tooth next to the post) but I had no pain. When I went back to my dentist he put on the permanent crown without filling the hole in the tooth under the crown. Is this normal? My tooth has been sore is it from the hole or the crown placement.