FROSTNIP
Frostnip is a superficial nonfreezing cold injury due to vasoconstriction. The skin will be pale and may have paresthesias or numbness. It is common on exposed skin including the cheeks, ears, and nose. The skin is still pliable. This is a major difference between frostnip and frostbite. If rewarmed at this point, there is no permanent tissue damage. If you identify a body part with frostnip, warm it immediately. Frostnip is a prescursor to frostbite and once recognized, appropriate precautions should be taken to treat it and prevent progression and recurrence.
FROSTBITE
Frostbite, unlike chilblains and frostnip, involves tissue freezing and can lead to permanent tissue damage. In this post, we review the pathophysiology and presentation of frostbite.
https://awls.org/wilderness-medicine-case-studies/cold-weather-injuries-frostnip-and-frostbite/