Čiernik was drafted as 216th overall in 1996 by the Ottawa Senators. He has played for the Washington Capitals and played a total of 89 regular season NHL games, scoring 12 goals and 14 assists. He has also played for Kölner Haie of the Deutsche Eishockey Liga (DEL) and for Sibir Novosibirsk of the Kontinental Hockey League (KHL).