Jack Butcher’s Mini Cooper was stopped by police on Morley Street, Kirkby, at 10.20pm, on December 30, 2016.
Officers smelled cannabis and a test revealed he had 3.1 microgrammes of the drug in one litre of blood, when the limit is 2 microgrammes.
He told the court he had been driving a friend who was smoking, but had not smoked any himself that day.
He said he had completely stopped smoking cannabis since his arrest, and didn’t realise it could continue to affect his driving.
Jack Butcher, 22, of Beacon Drive, admitted drug driving, and driving without insurance or a valid MOT, when he appeared at Mansfield Magistrates Court on Thursday.
He was fined £300 and ordered to pay £85 costs and a £30 victim surcharge. He was banned for 18 months.