It’s extremely difficult to force your nostrils to widen by simply picking them. The change in shape and size is due to other factors. The human body is often modified due by trauma. Picking your nose on a continuous basis may cause the scar tissue to form, essentially causing asymmetry of the nostrils. But asymmetric nostril sizes are typically caused by deviation of the caudal septum or asymmetric position of the medial crura. If you’re concerned about the shape of your nostrils, you can speak with an experienced surgeon so you can achieve the size and shape you’re looking for.