Wednesday night's quarter-final first leg result leaves the Catalan club in a strong position to reach the semis for the first time since 2019.
The return match is next Tuesday at Dortmund, who were last year's runners-up to Real Madrid.
"We played very well but we can't be thinking about the semi-finals yet," Lewandowski said.
"We scored four goals at home but we still have the return leg to play."
Raphinha added to his Champions League-leading tally by poking the ball into the open net in the 25th minute for his 12th goal in the competition this season. He than helped set up Lewandowski's first goal of the night in the 48th.
Lewandowski scored his 11th Champions League goal in the 66th before Yamal closed the scoring in the 77th.
The 36-year-old Lewandowski had scored 17 of his 105 career goals in the Champions League for Dortmund over three seasons from 2011-14.
The Poland striker, who is also the Spanish league's leading scorer this season with 25 goals, has 40 goals in all competitions.
In France, a wonder goal from Khvicha Kvaratskhelia upstaged a brilliant curling shot from teammate Desire Doue as Paris Saint-Germain beat Aston Villa 3-1 in the first leg of their quarter-final.
After Morgan Rogers gave Villa the lead in the 35th minute, the 19-year-old Doue drew PSG level four minutes later with the 12th goal of his breakthrough season.
Kvaratskhelia put the hosts in front four minutes after the break and left back Nuno Mendes added a third goal in added time with a fine finish of his own.
But Kvaratskhelia's was the goal of the night.
He sprinted down the left from just over the halfway line and then mesmerised Villa's defence in a blizzard of quick feet and superb balance.
Advancing at pace with the ball seemingly glued to his right foot, he then wrong-footed defender Axel Disasi with a sudden change of direction, before rolling the ball onto his left foot in one smooth motion and blasting an unstoppable shot over the head of goalkeeper Emiliano Martinez.
"For a coach like me it's so great to have a player like him, with his mentality. He scored a brilliant goal," PSG boss Luis Enrique said about Kvaratskhelia.
"We tried to sign him last summer and it didn't work out. We signed him (in January) when we didn't really expect to. He's got everything to be part of our project."
Villa coach Unai Emery has a tough task to overcome a two-goal deficit against the club he coached from 2016-18.
The return leg is next Tuesday in Birmingham.
