Mouth blisters - what are they?

I had an ingrown toe nail so I went to the doctors and he gave me some anti-biotics but last time I was put on anti-biotics for my tonsillitus I came up in a rash from head to toe and found out I was allergic to penicillin. About 2 weeks into taking the anti-biotics I started to get pain in my lip, I ate a packet of monster munch crisps that the doctor said started it off and inflamed the little blisters. I'm in excruitating pain! I can't eat because my gum is rubbing on my teeth :( and the doctor didnt know what it could be he suggested thrush but i searched up thrush and it looks nothing like thrush, it looks more like canker sores? do anyone know how to get rid of these?