The Red Devils were stunned by the French champions in their Champions League round of 16 showdown, despite PSG being without Neymar and Edinson Cavani.
Presnel Kimpembe and Kylian Mbappe netted in a 2-0 win at Old Trafford to end Solskjaer’s unbeaten run as Manchester United boss.
The Norwegian had won 10 of his 11 games in charge of United before their defeat against PSG.
Things went from bad to worse for United as Paul Pogba was sent off in the 89th minute for picking up a second yellow card.
And Solskjaer insists United’s defeat is a reality check for his Old Trafford stars.
“They had the momentum after the first goal and controlled the game,” he told BT Sport.
“You could see that we hadn’t played at this level for a while and we will have to learn.
“It was an experience that can go either way, it’s not going to be a season defining one, it’s one we have to learn from.
“Mountains are there to be climbed, you can’t lay down and say this is over We will go there, play our game and improve from today.
“Today is a reality check for us.”
Former United defender Rio Ferdinand echoed Solskjaer’s thoughts on the PSG win, adding a defeat may not necessarily be a bad thing for the Red Devils.
He said on BT Sport: “This is a reality check for this United team.
“It’s not a bad thing, it’s something to learn from. In this tenure Ole Gunner Solskjaer has probably been preparing for this loss.
“But tonight they didn’t show anything as an attacking force. They didn’t get around players.
“This PSG team, without two of their best attacking players, coasted.”
Phil Neville was also vocal after United’s defeat, insisting Solskjaer’s men have no chance in Paris in the second leg.
“I don’t think Manchester United have any chance in Paris [in the return leg],” he said. “PSG have too much European nous, too much class.
“Even though we didn’t see Mbappe at his absolute best, he was still devastating.”
United will now turn their attention to the FA Cup on Monday night against Chelsea before facing Liverpool in the Premier League.
The Red Devils travel to Paris for the second leg of their Champions League showdown with PSG on March 6.