Awoniyi fired home the winner for the Reds in first half added time.
Goldennewsng Reports that Harry Toffolo’s low cross found Jesse Lingard, whose shot ricocheted off a defender into the path of Awoniyi, who duly slotted the ball home.
Awoniyi was replaced by Samuel Surrige on 72nd minutes.
It was Nottingham Forest’s first Premier League goal at the City Ground since 1999.
Chris Bart-Williams was the last player to score at the ground on May 16, 1999.
The two teams had a goal chalked off for offside in the game.
Said Benhrama had a goal ruled out five minutes before the break, while Brennan Johnson’s strike was cancelled out in the 54th minute.
West Ham United missed the chance to equalise in the 64th minute when Declan Rice missed a penalty.