The Barcelona superstar netted Poland's second in a 2-0 win over Saudi Arabia on Saturday, four days after he missed a crucial penalty in his team's opening Group C draw against Mexico.
He slumped to the ground after scoring and was clearly in tears as he returned to the centre circle, with his goal ensuring Poland's hopes of progress to the last 16 remain alive.
"I think the older I get the more emotional I get, and I'm aware when it comes to World Cups it might be my last one actually," the 34-year-old said.
"After I scored, everything that I had inside - the dreams and also the importance of the goal, and how I scored - all those dreams from childhood were fulfilled and came true."
Just as Poland's first game hinged on a saved penalty, when Mexico's Guillermo Ochoa kept out Lewandowski's spot-kick, so did their second.
This time it was Poland's goalkeeper Wojciech Szczesny who proved the hero after Saudi Arabia were awarded the softest of penalties, saving Salem Al Dawsari's kick and then recovering to brilliantly tip over the rebound from Mohammed Al Burayk.
The former Arsenal number one was mobbed by his team-mates, with his heroics ensuring Poland went in 1-0 up at half-time after Lewandowski had set up Piotr Zielinski.
Lewandowski's goal sealed the deal eight minutes from time.
Asked about his star forward's emotional response to scoring, Poland coach Czeslaw Michniewicz said: "I was not surprised, because I know how deeply sad he felt in the last match. The whole team supported him.
"He could have had a hat-trick today and I'm so happy for him as we were very sad after he missed the penalty in the last game. But one player will not win the match alone, the force lies within the team and they were all fabulous, and Robert gave an assist to Zielinski and also scored so we are happy."
Saudi coach Herve Renard said his team had not put in an "efficient" performance, but he too was happy with his players despite the defeat, which followed on from the seismic shock of Tuesday's 2-1 victory over Argentina.
"We are still alive," he said.
"We will play until the last second of our World Cup, if it's next time (against Mexico) or another time, we won't give up.
"I'm just proud of them. I know them perfectly now. I know they are sad. Some of them feel guilty but football is a team game.
"Sometimes you get success, today we failed, so we are failing together. But we have one more game and I hope, a second one and maybe more. It's important to stay concentrated and think about November 30 (the game against Mexico)."