Am I obligated to undergo a surgical procedure on my face and lip to remove a birthmark and a deformity resulting from a previous operation, in order to please my parents and with the desire to get married, knowing that I made a covenant with Allah not to alter His creation? And will my parents bear sin if I do not undergo this procedure?

That which is forbidden among cosmetic surgeries is what is done to increase beauty and attractiveness. However, what is done to remove harm or treat a defect is permissible, as is the case with the questioner. This does not mean it is obligatory, so if the questioner wishes to remain as she is, there is no harm. As for the matter of marriage, it is a preordained provision, and undergoing the procedure does not necessitate it, nor does refraining from it necessitate its absence. There remains the matter of pleasing the father in this permissible procedure. As for vowing to Allah not to alter creation, its ruling is the ruling of an oath, and an expiation for an oath is due for it.