In reply to florence58:
If it hurts, rest it.
I know that sounds facetious, but honestly, your body will tell you when you should stop. If you head out in the cold and it's excruciatingly painful, then you need to head back and give your digets a break. If you can stay warm and you feel comfortable, then go for it.
As has been suggested above, cold injuries tend to compound the issue. Once you get nerve damage/frost nip/frost bite, that area of the body tends to be more prone the next time.