Aaron began his playing career with Heart of Midlothian’s youth teams, though he briefly played for Celtic’s academy teams. This year, while playing for Hearts against Celtic, he made history by becoming the youngest player to compete in a Scottish Cup final since 2008. In September 2019, Hearts defeated Hibernian 2-1 to win the Edinburgh derby, and he scored his first goal as a senior.

In July 2022, Aaron agreed to a four-year contract with Brentford.