Newcastle, though, lacked some impetus as a nine-game unbeaten run in all competitions came to an end, leaving them third in Group F, level on four points with Dortmund and two behind table-topping PSG.
“It was always going to be tight,” the Newcastle boss said. “There are top-quality teams in the group. Tonight is a blow, especially (losing) at home. A lesson in how fine the margins are going to be.
“The ball just wouldn’t go in for us. It was one of those nights. Callum had the first chance of the second half, that was a good one and then we hit the bar twice but just couldn’t force it in.
“Credit to the players, we never gave up, we kept doing the right things. We looked like a goal threat. But we have to be at our best to win and if you dip below that, it is tough to get results at this level.
“Any mistake you make is liable to get punished. We made one and seconds later we conceded so there is stuff we could have done better and when we analyse in the cold light of day, we will take a lot.”
A return trip to Dortmund in a fortnight’s time could prove instructive as to whether Newcastle will progress to the last 16 on their first appearance in Europe’s elite club competition in 20 years.
Their loss on Wednesday night was compounded by Alexander Isak limping off a quarter of an hour in with what appears to be a recurrence of a groin strain while second-half substitute Jacob Murphy was withdrawn five minutes after his introduction with a suspected dislocated shoulder.
“You look at some of the injuries, they are quite difficult to get your head around but we have to adjust,” Howe said.
“We can’t analyse too much, we have to regroup the players. We’re still in a very good position in the Premier League and Champions League.
“(The return game against Dortmund) is going to be hugely important. The next two away games, the league table looks very, very tight so they are great games for us, we have to approach them like that.
“Our lads are very honest and very focused on trying to win and achieve, there are some tired bodies and we have to recover for (the Premier League game at) Wolves (on Saturday).”
Dortmund head coach Edin Terzic hailed the display of Nmecha, who settled the contest after exploiting some space on the edge of the area and coolly slotting Nico Schlotterbeck’s cross beyond Nick Pope.
Nmecha, a former Manchester City youngster, was signed by Dortmund from Wolfsburg in the summer to fill the vacancy left by England midfielder Jude Bellingham, who left the Bundesliga club for Real Madrid.
“Felix is a brilliant player and we know about his potential and his talent and we knew he could improve our game – he had a fantastic game,” Terzic said.
“He finally managed to score, he had many opportunities in the first games of the season. This was a different role, he played more attacking. He had a rocky start in Dortmund and now he is in good form.”
As for Howe’s comments about Newcastle being given a lesson by Dortmund, Terzic responded: “That is nice to hear but it is just half-time, we face each other in a couple of weeks.
“We deserved in the first half and protected in the second half. We needed to be passionate, have some luck and a good goalie and we had all of that.”