During the opening 10 minutes, Southampton seemed to be well on top, but Forest grew into the game after a slow start and nearly took the lead against the run of play when Ryan Yates's shot fell to Brennan Johnson, but he could only hit the bar from close range.
Johnson made up for his previous miss by capitalising on the centre-back's error, racing through on goal and squaring the ball to Awoniyi, who coolly tapped home to net his fourth league goal of the season and give his side the lead.