Answer
The boiling point of nitrogen ($77K = -196^{\circ}C$) is too low. When a small amount of liquid nitrogen comes in contact with the skin, it will absorb heat from the skin and evaporate very quickly, causing little harm to the skin. The boiling point of water is $100^{\circ}C$. So, when a small amount of boiling water comes in contact with the skin, it releases a large amount of heat as it has high specific heat and does more harm to the skin than a small amount of liquid nitrogen.
Work Step by Step
The boiling point of nitrogen ($77K = -196^{\circ}C$) is too low. When a small amount of liquid nitrogen comes in contact with the skin, it will absorb heat from the skin and evaporate very quickly, causing little harm to the skin. The boiling point of water is $100^{\circ}C$. So, when a small amount of boiling water comes in contact with the skin, it releases a large amount of heat as it has high specific heat and does more harm to the skin than a small amount of liquid nitrogen.