It could be a generic throat infection or laryngitis. I get both a lot (no idea why!). Salt water gargles, warm drinks, and lozenges were my best friends. It can take a while for these things to resolve sometimes - dd1 is prone to tonsillitis but had a generic infection late 2013 which presented like tonsillitis and lasted for about 2 weeks.
I would be inclined to make the appointment and cancel if you feel better the day before.