Collins was ejected for the play.
Speaking publicly Wednesday for the first time since the incident, the veteran linebacker called what happened "a mistake."
He said he didn't believe he made contact with Kemp and he was trying to demonstrate what he believed Chicago running back David Montgomery had been doing -- lowering the crown of his helmet, which would be a penalty. Collins said he didn't agree with the ejection and that he believes he wasn't "a threat or anything towards him."
Collins said he wouldn't second-guess anything he did or said and explained that he "was demonstrating what the situation was, and I just so happened to bump the referee."
"Nothing was intentional, obviously," Collins said. "It's crazy [that] a person like me would ever, so they say, headbutt a referee. It wasn't intentional. It is what it is. They called it. They threw me out. Can't do nothing about it but take it on the chin and hope for the best, get ready for next week, or this week, shall I say."
Kemp said in a pool report after the game he believed Collins' actions were "unnecessary." So he called a penalty and then decided to eject him, ruling "unnecessary contact."
Lions coach Matt Patricia said he spoke with Collins and the entire team about the ejection after the game and made it clear you can't touch officials.
"There's rules in place for a reason, and it's to protect everyone that's out on the field, including the officials, and everybody knows that," Patricia said. "Whether it's an honest mistake or not, you just can't do that, and that's the bottom line."
It was Collins' first game for the Lions after coming over from the New England Patriots in free agency.