Curiously enough, Mr. Kitchen, it isn't really a nomination of the House of Commons. It's actually a motion, and there is no such provision. Once the motion is made, it's in the hands of the committee. You would have needed unanimous consent to withdraw. Your only option now, if you don't want to be chair, would be to resign. However, there is unfortunately no provision for us if a candidate accepts a nomination.
On October 8th, 2020. See this statement in context.