Sore on 4 year olds tongue.

Sorry for the graphic image but i needed to show how bad it is. My son was up all night crying that his tongue/teeth hurt last night. I noticed some bumps on his tongue this morning but thought maybe he bit his tongue. I kept him home from daycare and he was fine all day. When he was brushing his teeth tonight i noticed a HUGE sore on his tongue and it goes all the way down one side! It looks way too big to be a canker sore and I'm super worried. I'm taking him to urgen care tomorrow when they open but anyone have any idea what it could be? :( (the white on his lip is leftover toothpaste)