I believe it is country wide as I know quite a few people from different parts of Poland
Traditions are usually observed in countryside, not in the cities.
Courtesy of Polish Wikipedia (The English one focuses on other parts) and my hasty translation:
Saint Nicholas (Polish: Św. Mikołaj), Bishop of Myra, because of the deeds attributed by the legend (including distributing all his property to the poor), was the prototype of a dealer of gifts to children. Depicted as an old man with a magnificent beard, often in the miter and crosier, with a sack of gifts and a bunch of rods in his hand. He brings gifts to good children (usually sweets) and rods to the naughty, as the warning, on December 6 (the anniversary of the Saint's death).
One legend has it that a man who fell into poverty, decided to sell his three daughters to a brothel. When the bishop learned of this he threw three purses of money in the chimney at night. They fell into stockings and the shoes that these daughters have put at the fireplace to dry. Hence, in countries where it is common to use fireplaces, children put their shoes and socks near the fireplace. Where fireplaces are not used, St. Nicolas quietly slips gifts under the pillows of sleeping babies.
In most of Poland it is Sw. Mikołaj that brings gifts on December 6.
In Wielkopolska, Kujawy, Kashubia and Western Pomerania gifts for Christmas traditionally brings "Gwiazdor", in Małopolska - Little Angel, in Upper Silesia - Little Jesus. Which I did not know; in my family Św. Mikołaj worked double shift.