Hi..thanks for your query. It is important to identify the cause of lip swelling you are having. One of the most common causes is Herpes simplex infection or cold sores.This occurs under stress ,as might be due to the surgery you went through.It will require appropriate anti viral therapy and topical antibiotic therapy.You can apply antibiotic ointment twice daily on the lips to treat/prevent superimposed infection.Other causes of lip swelling are Angioedema (secondary to medications).If the swelling is persistent , you should visit a dermatologist for an appropriate diagnosis. Hope this is helpful,take care!