I'm going to assume that you went back to the Dermatologist who did the TCA peel and asked about this???   I'm also guessing that he/she didn't run the peel solution down just over the vermillion border (the edge where the lips and skin meet)??    Usually we apply the peel solution just over the border onto the lips about 1-2 millimeters to avoid this problem.  Your doctor should be able to go back and carefully peel just the area where the problem is.   If you have any history of cold sores ever, be sure to take the prescription tablets (Famvir, Valtrex or acyclovir) prior and during the peel.  Peels on the lips will activate cold sores.   Hope this helps, Dr. I