Lewandowski, signed from Bayern Munich in the summer, scored his first Barca goal within the first minute of the match, only for Alexander Isak to equalize five minutes later.
With the scores level, France international Ousmane Dembélé appeared to catch Sociedad defender Aihen Muñoz in the face with his elbow.
Dembélé avoided a red card and, in a cruel twist of fate, scored Barcelona’s second goal of the game after a sumptuous backheel from substitute Ansu Fati.
Fati’s second-half introduction proved even more important as the 19-year-old netted Lewandowski’s second goal of the night on a plate before grabbing his own to make it 4-1 .
Lewandowski himself is full of praise for his new teammates after scoring his first two goals for the Catalan club.
“The first goal I score for a new team is always for my father, who is watching from the sky,” he said after the game. “It was amazing, I’m very happy and proud of the team because in the second half we were playing very well and we scored four goals. Now we’re going back to Barcelona and we’ll enjoy it for the next few days. “
He added: “The first game [against Rayo Vallecano] was not good, everything was new. In the first weeks, we have to get to know each other and each game will be better. There are a lot of youngsters I have quick chemistry with on the pitch.”
It was the story of a 34-year-old veteran striker and a 19-year-old prodigy.
After a stunted start to the season last week in their goalless draw with Rayo Vallecano, manager Xavi’s side began to show a glimpse of what it could be on Sunday.
With a mix of non-club experience – Lewandowski and Christensen – and a host of academy graduates – Pedri, Gavi, Ansu Fati and Alejandro Balde – Xavi’s side have huge potential.
And from the first minute at the Anoeta Stadium, it looked like everything was going well, as 18-year-old left-back Balde raced down the wing before crossing the ball for Lewandowski to head home.
But Barca were caught minutes later. Frankie de Jong was taken into possession before Isak slipped, the Swedish striker’s shot passing over Marc-Andre ter Stegen in goal.
And Barcelona could have – and perhaps should have – been reduced to 10 men when Dembélé appeared to elbow Muñoz in the face, but the video assistant referee opted not to review the incident and Dembélé walked away. escaped without even a yellow card.
After half-time, and after Fati’s introduction in the 63rd minute, the game tipped in favor of Barça.
Fati, who is coming back from a lost season due to knee injuries, used his pace and exuberance to dissect Sociedad’s defence, finishing the game with two assists and a goal.
After the game, Xavi said he was “very happy” with the win.
“Sometimes we had to be more patient – sometimes we are too brash because we play with very young players,” he said.
“But I’m very happy, this victory shows that we are on the right path; the result last week was a bit of a blow and winning here strengthens us… You had to be brave after not winning the week last and the bet came out well for us.”