The Manchester City loanee missed three matches, including two encounters against Newcastle United and a victory over Coventry City.
However, the 31-year-old returned to action on Thursday, featuring in a behind-closed-doors friendly victory against Derby County.
Grealish subsequently expressed regret on social media, insisting he cannot wait to play before Everton supporters again.
"Nice to be back out there with the boys today after a good few days training," Grealish wrote on his Instagram story.
"I want to apologise to the fans and everyone at the club for not being able to help the team the last few weeks.
"I love playing for this club and can't wait to be back playing in front of you guys in an Everton shirt. See you soon."
Everton are next in action against Brentford on Monday, November 23rd.
