Cutting your toenails too short, particularly the sides of your big toe, can result in the nail curling down and digging into your skin, causing and ingrown toenail. Trimming your nails so they curve with the shape of your toe also exposes your nail bed, which can lead to fungal infections developing under the nail. Toenails should not be cut shorter than the edge of the toe and should have a straight, not curved edge.