How to cut toenails properly
Many people will have an ingrown toenail at some point in their lives. Using the right technique to cut your toenails can help prevent this problem, though.
It’s important to make sure that you cut your toenails straight across, leaving them long enough so that the corners lie loosely against the skin at the sides.
In other words, don't trim your toenails too short, don't round the edges, and also don't try to cut the toenails into a pointy V-shape.