Cardiff born inside right Jack Nicholls played for Ton Pentre in 1920, Cardiff Corinthians in 1921, and Pontypridd and Bridgend Town in 1922 before joining Third Division (South) Newport County, for whom he made his debut at Plymouth Argyle in December 1923, scoring twice on his debut in a 3-2 defeat. Having established himself in the Newport side, Nicholls was handed his debut for Wales on 3rd March 1924 in a 2-1 victory over England in the 1924 British Home Championship, becoming the first Newport County player to gain an international cap, winning a further cap .
He was released at the end of the 1923-24 season and signed with First Division Cardiff City. He made his debut in October 1924 in a 2-1 win over Newcastle United but he went on to make just one more appearance for the first team two weeks later in a defeat at Nottingham Forest before leaving the following year. Despite being unable to break into the Cardiff first-team, Nicholls gained his last two caps for Wales while at Ninian Park, playing in a 3-1 defeat to Scotland, in a team that contained five Cardiff players, and a 2-1 defeat to England during the 1925 British Home Championship.
He spent 1925-26 on the books of Swansea City but didn’t manage to get into their first team, and in 1926 he re-joined non league Cardiff Corinthians. He played 10 amateur internationals for Wales between 1923 and 1930, scoring 5 goals, and is the joint highest Wales Amateur international scorer.
His father Sydney Nicholls and uncle Gwyn Nicholls were both Wales rugby union internationals.