so it came away in one chunk? You might find you have a bent pin or two then

Do you have a thin plastic item that could be used to slide between the cpu and hsf? A credit card it too thick... like a dummy credit card (they are thin but quite tough). Put the hsf on it's side, holding the hsf only, slide the implement between, careful but firm pressure and have a motherboard anti static bag near the cpu side to catch it...