The midfielder was on target against Bolton Wanderers on Sunday, scoring with a volley in the 79th minute to put his side in front - but two late goals gave the Trotters a 3-2 victory which preserved their Sky Bet Championship status.
Colback, who joined Forest in January, made 16 league appearances.
While his loan spell has now come to an end, Aleksandar Mitrovic's time at Fulham will continue for another few days as the Cottagers missed out on automatic promotion.
A 3-1 defeat at Birmingham means they will take part in the play-offs, and will meet Derby County in the semi-finals. Mitrovic played the full game but failed to score for the first time in four matches.
Blackburn, meanwhile, couldn't clinch the Sky Bet League One title on Saturday despite beating Oxford 2-1. Wigan's win at Doncaster saw them lift the trophy, but Rovers still went up in second place.
Adam Armstrong's nine goals have been crucial and he made his 21st appearance for Rovers (17 from the start) at the weekend. He came off in the 78th minute, just after Tony Mowbray's side had scored their second.
Elsewhere in League One, Alex Gilliead made his 48th appearance of the season for Bradford in a 1-1 draw at Scunthorpe. He played for the opening 62 minutes, while Ivan Toney was not involved for Scunthorpe, who will compete in the play-offs later this week.
Sean Longstaff played for 67 minutes as Blackpool lost 1-0 to Rotherham. Longstaff scored nine times in 45 league and cup appearances for the Tangerines.
In League Two, Crewe Alexandra named a starting XI made up entirely of homegrown players, meaning Jamie Sterry was an unused substitute as they beat Cheltenham 2-1. Sterry made nine appearances during his loan spell.
In Scotland, Stuart Findlay played the full game as Kilmarnock lost 1-0 to Rangers while Freddie Woodman was an unused substitute for Aberdeen, who drew 0-0 with Hibernian.
Henri Saivet completed 90 minutes for Sivasspor as they drew 1-1 with Istanbul Basaksehir in the Turkish Super Lig, while Matz Sels was in goal for Anderlecht as they beat Club Brugge in the Belgian league play-offs.
But there was disappointment for Hellas Verona and Rolando Aarons, as the Italian side's 4-1 defeat to AC Milan confirmed their relegation from Serie A. Aarons came on in the 76th minute.
