Paul Lewis's Ford was stopped on Ambleside in Gamston after police spotted his nearside headlight wasn't working, just before 4am, on October 13 last year, said prosecutor Robert Carr at Nottingham Magistrates Court.
But they smelled cannabis coming from the car and said he “appeared to be under the influence of something.”
A test revealed the drug in his system was over the prescribed level.
Ian Boddy, mitigating, said: "I do have some sympathy for Mr Lewis. All the education is about alcohol and there's absolutely nothing about drugs. Cannabis stays in the system for ten days."
He said Lewis argued with his partner the night before and smoked cannabis to calm down because he was upset.
"He was driving to work in Gamston," Mr Boddy said. "There was no problem with his driving."
He added that the loss of his licence would be “devastating” for Lewis, who works as a forklift truck driver for a firm in Gamston.
The court heard he had been getting supplies to elderly people during the lockdown and his reputation in the local community was "second to none."
Lewis, 39, of Abercorn Close, Bulwell, pleaded guilty to the driving offence at Nottingham Magistrates Court, on Wednesday, March 10.
He was fined £200, and was ordered to pay £85 costs and a victim surcharge of £34, which he will pay off at £50 per month.
He was banned from driving for 12 months.