A large nostril and a small nostril may be congenital malformation, trauma, intranasal swelling and other diseases. 1. Congenital malformation: some patients are born with two nostrils that are obviously not the same size, which may be related to embryonic developmental deformity or extrusion of the nose at birth. 2. Trauma: when there is obvious crack in the external or internal nose, after suturing, scar tissue proliferation can cause one side of the nostril to shrink; some patients are bitten by “rats” and other creatures, and when the trauma is large, the scar shrinks after healing, and the nostrils may shrink in size. 3. Intranasal swelling: If there is a cyst or tumor in the nasal vestibule, it will block the anterior nostril, and the size of nostrils on both sides will be different. Therefore, if you have any of the above factors, you should go to the hospital in time to get a clear idea of the cause and follow the doctor’s instructions.