Cherry wrote later, "During these days the blisters on my fingers were very painful. Long before my hands were frost-bitten, or indeed anything but cold, which was of course a normal thing, the matter inside these big blisters, which rose all down my fingers with only a skin between them, was frozen into ice. To handle the cooking gear or the food bags was agony; to start the primus was worse; and when, one day, I was able to prick six or seven of the blisters after supper and let the liquid matter out, the relief was very great. Every night after that I treated such others as were ready in the same way until they gradually disappeared. Sometimes it was difficult not to howl." 
Blistering is in fact a symptom of relatively shallow frostbite, deeper than when the skin becomes numb and white, but not as bad as when the affected area turns hard and, in worst cases, black.
 Scott Polar Research Institute.
 Apsley Cherry-Garrard, The Worst Journey in the World, ch.VII.