Hi. Thanks for your query. Noted the history and understood the concerns. A small pea sized purple bump in the belly button is usually due to an umbilical granuloma. And I would advise you the following for such a lump. Since you have already been examined by a Doctor and are scheduled for surgery, this looks to be not amenable to regular cleaning with hydrogen peroxide, application of Liquid Povidone Iodine and dressings. It is the best way to get this operated out to get the proper and complete cure. I am sure the Surgeon will do the full justice by operating properly so as not to disturb your umbilical structure. Go for surgery.