Leeds dominated the clash but could not force home their advantage and missed the chance to close the gap on the automatic promotion places.
Christiansen said: “Clearly that’s two points we’ve dropped. We didn’t deserve to win the game on Saturday (against Birmingham). We didn’t deserve to get anything that day, but here we did almost everything to get the victory.
“It seemed like there was a wall inside their goal at times. We created some big opportunities to score, but on this day, unfortunately, we’ve only done enough to get the one point.
“Credit to Nottingham Forest. They have been in a difficult situation recently, but they put in a good performance.
“They took what they came for and that was a point. For us it’s not enough of course, but we have to move on to the next game now.”
Forest defender Kieran Dowell cleared Pontus Jansson’s goalbound header off the line early in the game, with Kemar Roofe scooping the rebound over the crossbar from inside the six-yard box.
In the second period, Leeds frontman Roofe was unmarked 15 yards from goal but could only sidefoot a shot against the crossbar.
At the other end, Forest’s Ben Osborn fired in from distance only to be denied by a terrific diving save from Felix Wiedwald. The German goalkeeper was then called upon to make a smart save to keep out Dowell’s drive.