I Went To A Dentist For A Tooth Ache Two

I went to a dentist for a tooth ache two days ago and he said that I need a root canal for a tooth with a deep cavity on lower right side. I have been having ear pain and sore throat kind of sensation on the right side because of the cavity. The pain became worse since two days ago and now I am taking Advil every 6 hours but worried that the pain is just get worse. I could not find any dentist near my home who can take me in for emergency. The earliest time i can see a dentist is tomorrow morning. I really don't want to visit regular emergency hospital for this if I can avoid it. I have some left over Amoxicillin 500mg that was given to my by a dentist before. Should I just take it to prevent the infection gets worse today or should I wait until tomorrow morning to see the local dentist? How fast can a tooth infection develop and how bad does it have to be before I take Amoxcillin?