The 20-year-old captain headed the Rams into the lead midway through the first half and doubled it in the middle of the second period, before Lewis Walters pulled one back for Forest.
Derby top Group A with 12 points, three ahead of Birmingham City, who have three more than Forest.
Forest can still go through if they win their final group match at Middlesbrough.
Nott'm Forest: 26 Feb v Middlesbrough (A) PL Cup
Derby: 19 Feb v Everton (A) PL2