Blisters in the corners of my mouth/lips and dentists...query?

SO I went to the dentist on Monday to have an impression done for a night-guard and it was a horrible experience. It’s a new dentist that I have just been assigned to (because I’m on benefits I don’t pay for NHS Dental treatment but I’ve been with a private dentist until now…) and have not been at all impressed by the quality of care but anyway…

The dentist didn’t even know what she was supposed to be doing…she started doing a check up and had to be told 3 times that I was there for impressions. Then they couldn’t get the mixture right. and then the mould that she literally shoved in my mouth seemed way to big.

Anyway I woke up yesterday with really really painful corners of my mouth… you know where the top lip joins the bottom lip at the sides. By lunchtime blisters had appeared. My lips are swollen slightly on the inside too and feel bruised.

It seems silly to go to the Doctor for something like this. What is this? I’ve NEVER had cold sores (even when dating boyfriends with them) so have they infected me…. or are these blisters something else? I’m a bit concerned about what I should do about them…and about the incompetent dentist!!!

grrrrrr