Huntelaar scored Milan's equaliser in the 81st minute, setting up a thrilling finish as Alexandre Pato grabbed a winner in stoppage time.
Speaking to Milan's official TV channel, he said: "After my equaliser in Florence, I literally went crazy with joy.
"It was a very important goal in a difficult moment of the game. My celebratory gesture was one of joy and liberation with respect to the many minutes in which we were a goal down, but it was absolutely not meant to be offensive to the opponent's fans.
"I am really sorry if it has been seen in this way."