While Michael O’Neill’s side were going down 3-1 in Germany, Slovakia jumped to the top of the table thanks to a 90th-minute winner in Luxembourg.
It means two games into the campaign, Slovakia have six points, Northern Ireland and Germany have three and Luxembourg are on zero.
In October, Northern Ireland face the Slovakians and then the Germans at Windsor Park.
“It’s all about the three points and Slovakia managed to get that (in Luxembourg). That just means even more that we’ve to go back home and beat them,” said Charles.
Like his team-mates, the Southampton midfielder was disappointed not to have anything to show for the side’s efforts versus Germany in Cologne after fighting back to level terms having conceded early before letting in a couple of goals in quick succession in the second-half.
We are disappointed to come away with nothing from the game.
“Despite the level of players they (Germany) have, I think we completely matched them,” said Charles.
“They had all the ball, but we did well at winning it back and breaking them down. The times we conceded were a killer. If we get to the 70th minute at 1-1, we’d have a very good chance.
“We are disappointed to come away with nothing from the game. Conceding the early goal, we almost gifted it to them. That was also disappointing.
Northern Ireland pair Shea Charles (left) and Ali McCann put pressure on Germany’s Florian Wirtz (Getty Images)
“I think early on, away from home, we did very well not to crumble and come back and go in at half-time at 1-1.
“In the second-half, again, we gave them a goal and then they scored a good free-kick and that was that.”
Charles added that the team can take heart from large parts of their game in Germany.
“To do that away from home, we’ve come a long way as a group,” he said.
“A couple of years ago, we’d have been, not happy, but not disappointed with that result. The fact that we are disappointed and annoyed at losing that game I think is really good to see.”