The own goal proved to be the victor.
The ball made its way outside the 18 as Lukaku maneuvered toward an onside position after swinging his right and then left leg at Bong, who appears to block a very sensitive region with his hand.
The incident during United's 1-0 win over Brighton appeared to go unseen by the match officials.
Lukaku appeared to twice swing a leg at Bong as the two players came together in the build-up to United's victor on the day, but referee Neil Swarbrick took no action.
The 54-year-old United manager added that, in the last minute of the match, Lukaku, "was fighting and running back like he was in the first minute".
Fortunately for him, he will get another chance today, should he play against Watford.
The Belgian's recent goalscoring record has dropped significantly from the start of the season, when he netted 11 times in his first 10 games for the club following a £75m move from Everton in the summer.
"Players are men, men are different, men are unique cases and some guys are capable of going into their limits of effort and some other guys, even with a lot of talent, they don't manage to do that. He didn't score, but I don't care".