The inside of the nose is covered by a thin mucous membrane, and the blood vessels in the mucous membrane are very thin and easily broken. The blood vessels in the nose are very thin and easily broken, and one of the most easily broken blood vessels is located just inside the nostril.
When you pick your nose or put your finger in the nostril, you will find the weak part right where your fingernail hits it. Therefore, if you scratch the area with your fingernail and cause a scratch, the blood vessel will break immediately and blood will come out. In addition to scratching with the claw, nosebleeds can also occur if the nose is bumped strongly. This is also caused by the blood vessels in the nose being broken by the bump, resulting in blood.