Dentists see people that come to them too late all the time. So you don't have to be scared of that part, they are not gonna be mean because of that or something. And if you go later rather than in a couple of days, it might be a much worse visit. Loads of people are scared of the dentists and I'm sure if you let them know, they will ensure that you can feel as comfortable as possible! It's good to take care of you, which includes going to doctors and dentists when there's problems.