Dear Hanne91;
Your nostrils are quite wide and the overall width of your nose, compared to the entire width of your face, is rather significant. Smiling probably makes it worse because the cheek muscles pull the wings of the nose up and out to further widen the nose.
If your bridge is low, you may be well served by having the bridge improved either using natural tissue or an artificial bridge. And there may be a place to narrow the floor of your nostrils. Likewise, the tip might stand a little narrowing. However, none of those things will prevent the nose from widening with smile. Remember, other people have a problem where the tip of the nose depresses with smile; that is correctable. Unfortunately, one cannot sever or paralyze the muscle that tend to widen the nose when smiling.
Robert Kotler, MD, FACS
Facial Plastic Surgeon
Author, SECRETS OF A BEVERLY HILLS COSMETIC SURGEON
Author, THE ESSENTIAL COSMETIC SURGERY COMPANION