Last week I went to the dentist and got a deep filling, which the dentist said was extremely close to needing a root canal. He put some kind of core or material in the tooth, did a filling and binding (i think that's what he called it). My tooth has been fine ever since except it has been a little painful to chew on hard or crunchy foods. Tonight, I have a slight discomfort and pain in the tooth. It is the back tooth on the top left. Should I be concerned?