He said he only did so because the Premier League had forced the club's hand on the matter.
Megson explained: "I had been working up until 10 days ago without signing anything although obviously I have been getting paid.
"It is not such a big thing. It was just a pre-requisite from the league. So I had to do what I was supposed to do.
"There is no difference to the way I have been working and gone about things. All I have done now is sign a bit of paper."
Megson feels Bolton are on the right path after he managed to steer the side clear of relegation against the odds last season.
He said: "I do not want to harp on about it but we were in a mess 16 months ago.
"I think 22 players have left and maybe 10 or 11 have come in to replace them. We are actually in the black.
"We have to get it right on the football pitch and financially. I feel we are doing that but we can't afford to make too many mistakes financially. We can't go bananas in one go.
"We are doing a little bit better than last season and have the opportunity to finish strongly and I certainly hope we do that."
Gardner broke Newcastle's resistance with a superb strike following a cross from Matt Taylor in the 46th minute.
That was enough to give Bolton victory and put them in good heart for the trip to Stoke on Wednesday.
Megson said: "I was quite pleased with our performance in the first half although we did not show enough penetration. But we looked quite solid.
"They did not cause us too many problems from set-pieces. We obviously got off to a great start in the second half and scored.
"But after that we didn't pass the ball well enough and did not keep it enough. However we made the point before the game that the result was all-important and it was the right one."
Newcastle caretaker-boss Chris Hughton felt his side should have had a penalty when Jlloyd Samuel blocked Fabricio Coloccini's effort.
However, referee Alan Wiley waved play on, leaving the visitors furious.
Hughton said: "I thought the lad's hands were out and it was one a lot of referees would have given."
Striker Obafemi Martins was also out of luck with a couple of efforts and looked unhappy when he was replaced by Mark Viduka.
"Oba has been out of action for some time and perhaps lacked that bit of sharpness," said Hughton. "That's why I made the change."
Newcastle remain in trouble and skipper Nicky Butt limped off with a knee injury while Damien Duff was sidelined with a calf problem.
Hughton added: "We gave a spirited performance and had better opportunities than Bolton.
"We just lacked a bit of guile and composure to break them down. The goal galvanised them a little bit but I felt we should have had something from the game."