After Dean Bowditch’s ninth-minute goal, Boro prodded and probed to no avail until Jordan Rhodes climbed off the bench to head a last-gasp equaliser.
Karanka said: “It was an amazing, massive point because this game was tough and every single game is going to be really tough from now until the end.
“So for this reason the main thing is we are at the top of the table with a game in hand so I am really pleased, the players are really pleased.
“If we had scored at the beginning of the second half we would have won the game for sure.
“When you have the players I have on the pitch when we are in the box we are going to score goals whether it is at the beginning of the game or the end of the game.
“We have to keep going, the last three or four games haven’t gone the way we would have wanted but sometimes I think we forget which position we are in because we are now in an amazing position.
“If you had said to me or the supporters in the summer that we could be in this position at this time of the season, we would have signed up for that.”
Middlesbrough are a point clear of Hull at the top of the table, while at the other end MK Dons are three points clear of the relegation zone in 20th.
And Dons manager Karl Robinson admitted the late sucker-punch from £9million-man Rhodes was hard to swallow.
“I’m gutted,” said Robinson. “I said to my staff that we might have scored too early against one of the best teams in the league.
“I’m so proud of the players but one individual error has cost us again. That’s the man in the middle.
“Josh Murphy should have had a blatant penalty in the first half, and the referee is looking right down the line. They’ve got a massive slice of luck with that.
“We should have had a penalty on Saturday and we should have had one here. This is a young kid learning the game and I can’t wait to get downstairs and speak to the referee.
“I don’t know what he’s seen, the player has touched it to one side, the ball isn’t out of play and he’s been clattered. We got no decisions, we were the little team on the pitch and it felt like that.
“We tried to match Middlesbrough at their own game, but you look at their team and their squad list in front of you and it’s daunting.”