The result gave the hosts a nine-point cushion over the relegation zone with six games remaining, but Metgod accepts his side cannot afford to think they are safe just yet.
"It would be foolish to think that," he said. "This was a massive step in the right direction today but we have still got a bit to do.
"I would like to be on the safe side and get to 54 points. I can't see any reason why we can't win in the next two games and then hopefully start thinking about other things after that.
"But we are not there yet and we have to be careful not to think along those lines. This is a massive win and has given confidence to everybody."
Metgod reckons Derby were overdue the slice of luck that arrived when Weale blundered in front of more than 3,000 Leicester fans.
"Today, on March 27, we had our first bit of luck this season," said the Dutchman. "It's about little details in football and they win or lose you a game.
"You have to grind, graft and work hard to get into those positions to be lucky. It's very unfortunate for him (Weale) but I am just delighted it went our way.
"I didn't see it coming. I expected him to clear it. I don't know whether the ball bobbled or he just missed it but I couldn't care less really!"
Leicester player-coach Chris Powell backed Weale to bounce back from the error.
The former Derby defender said: "I have seen or two incidents like that but what I will say is that Chris Weale has been quite outstanding this season.
"He's been one of our major players and he's got the mental capacity to bounce back. He made one or two good saves after that which shows the quality of the man.
"It was a freak goal that separated the teams and I thought Derby were resolute and dogged in their defending but we played into their hands a bit. We should have changed the way we played.
"It's now up to us to regroup and come back and perform the way we can. We lost on Wednesday and now today and we have to arrest that slide quickly because every game now will have something riding on it."
Derby could not have expected the gift Weale presented to them in the 20th minute.
Paul Green's innocuous ball into the box was played back by King for what should have been a routine clearance for Weale, but he somehow allowed it to roll over his boot and over the line.
It was a startling error by the keeper and, not surprisingly, knocked the play-off-chasing visitors back.
Derby were close to a second minutes later when Chris Porter got in on the right but a heavy touch gave Jack Hobbs the chance to clear.
Leicester had created little despite some neat passing moves and it was Porter who carved out another opportunity when he span away from Wayne Brown on the Derby right but his low cross was cut out.
Stephen Bywater preserved Derby's lead in the 43rd minute when he dived to his right to push away a 20-yard Richie Wellens shot which was the visitors' first effort on target.
The quality of the game did not improve in the second half although Derby still looked more likely to add to their lead with Stephen Pearson wasting a good chance when he lost control of the ball.
Porter fired over from the edge of the box before Leicester introduced former Derby striker Steve Howard in place of Martyn Waghorn after 62 minutes.
Howard almost set up an equaliser in the 83rd minute when he headed a Paul Gallagher corner to Michael Morrison whose close range flick went into the arms of Bywater in what turned out to be their last chance to salvage some local pride.