The Red Devils entered a heavyweight continental clash unbeaten through 11 games under their interim boss.
Confidence was high at Old Trafford, especially as the visitors were without the injured Neymar and Edinson Cavani, but Solskjaer’s bubble was burst against the Ligue 1 title holders.
Presnel Kimpembe and Kylian Mbappe got the goals for PSG, before Paul Pogba compounded United’s misery by collecting a late red card which will keep him out of the second leg.
The Red Devils also saw Jesse Lingard and Anthony Martial pick up untimely knocks on a forgettable night which extended their long wait for a victory in the knockout rounds of the Champions League.
Solskjaer told BT Sport afterwards of the challenge facing his side: “It looked like the game we thought it was going to be. The first goal, when they got that one - it's a poor goal to give away - then they got the momentum.
“You can see that we've not played games at this level for a while and we'll have to learn from this experience. It's not going to be a season defining one for us.
“Mountains are there to be climbed. You can't lie down. Today was a reality check on the level from the top teams.”
Solskjaer added on the knocks picked up by two in-form performers, with Lingard and Martial forced off at just before and during half-time: “They're muscle injuries so we have to wait a couple of days.”
The United boss refused to blame the loss of a key pair of performers for a second-half showing which saw European ambitions suffer a heavy blow.
He said: “You can't say that's the reason because we had [Juan] Mata and [Alexis] Sanchez to come on, they're quality players.”
It remains to be seen whether Lingard and Martial will be available for a return date at Parc des Princes on March 6.
France international Pogba will definitely not be playing any part when he heads back to his roots in Paris, with the World Cup winner set to serve a ban.
He was dismissed after tangling with the vastly-experienced Dani Alves, with the Brazilian caught on the knee by a high boot.
Solskjaer said of the straight red card shown to a midfielder who has put in a string of inspirational performances of late: “He's trying to get his body across and Alves is clever enough to put his foot in there so it hits him.”
United will be looking to put the disappointment of a frustrating night in Europe behind them as quickly as possible as the big tests keep on coming, with Chelsea next up in the FA Cup fifth round before Premier League title chasers Liverpool pay a visit to Old Trafford.