<s>[INST] I had a temporary crown placed on Monday (lower back molar) I developed a blister on the gum behind the tooth 2 days later.  The blister is now higher than the tooth.  White, no pus.  Some swelling.  Not a lot of pain.  Could it be from an injection site or should I be concerned about an abscess? [/INST] Hello, Welcome Thanks for consulting Chat Doctor, I have gone through your query, as you have swelling on gum it can be due to deposition of food, so there can Periodontal pocket formation or due to formation of Periodontal Abscess also.  Go to dentist and go for IOWA if necessary, then go for treatment Scaling and curettage.  Do warm saline gargle two - three times a day.  Hope this will help you. Wishing you good health. </s>