The midfielder was penalised for handling the ball in the penalty area after Aaron Wan-Bissaka's header hit his fingers. Referee Paul Tierney did not notice the incident in real time, but was soon instructed by VAR to take a second look via the pitchside monitor and duly awarded a spot kick.
Gundogan added his and his team’s second goal shortly after half-time, and Grealish has thanked Gundogan for "saving" him as City went on the lift the trophy.
"I obviously give away the penalty ... I don't know how it's a penalty, I'm not even looking at the ball,” he told BBC Sport.
Grealish then reenacted his body movement during the incident, while adding: "I've missed the ball with my head, and [Wan-Bissaka] has headed it. I can understand if I've blocked a cross [while] looking at it... anyway, Gundo saved me."
Next up for City is the Champions League Final on June 10 against Inter Milan.