The midfielder was shown the red card after he appeared to kick the youngster for failing to return the ball quickly during the League Cup semi-final.
"They both recognise there was a mistake," Benitez told BBC Sport.
"The boy was apologising for time wasting. Hazard was frustrated and tried to get the ball. He was kicking the ball and getting the ball.
"We can analyse if for half an hour but we know that both are wrong."
The game finished in a 0-0 draw meaning Swansea progress to the final 2-0 on aggregate. They will meet League Two outfit Bradford City at Wembley.