Ćwielong was born in Chorzów. At the age of seven he started playing for Ruch Chorzów. Four years later he moved to Stadion Śląski Chorzów – a club known for developing young players. In 2004, he returned to Ruch Chorzów where he played 132 matches and scored 32 goals. Ćwielong scored his first goal for his new team against Pogoń Szczecin at the age of 18.