But considering the place you said :
Not staying in one place -> no mining -> no metals -> Stone Age forever
, plus a polar temperature, I would say you want something like Antartida or Greenland, or even north of Russia, where there are no people living permanently till these days, what means that living on places like that on a medieval era would be basically impossible. If there was mining at least they could have some sort of trade agreement with another faraway civilization, trading metals for food by sea. But with nothing, being on Stone Age forever I really can't see anything working on a "close-to-medieval-aged-earth" world, unless as I said before you introduced magic on it, than it is a whole different thing...