West Brom manager Gary Megson defended his player saying he was probably unfamiliar with Forest's "multi-ball system" although they were told about this prior to Saturday's kick-off.
He said: "What happened with the ballboy when he was shoved shouldn’t happen.
"The reaction was because the ball didn’t come back as it had been doing throughout the game. It was more out of frustration than nasti-ness."
Forest's goal came from the penalty spot after Geoff Horsfield tangled with Forest right-back Matthieu Louis-Jean. The West Brom players felt they had been hard done by and Baggies' £1m signing even picked up a caution for dissent.
Forest manager Paul Hart believed the penalty award was the correct one and was also upset with the ballboy incident.
He said: "I saw the ballboy get pushed.
"The rules are clear that he shouldn’t release the ball until another one has come back."
The FA Cup 4th Round draw takes place on Monday 5 January at 1pm.