The Borussia Dortmund front man refused to confirm Poland coach Franciszek Smuda's suggestion earlier this week that he would be playing at Old Trafford next season
Lewandowski said: "I am so happy to score this goal in the opening match. But I'm not going to concentrate on these issues (joining United). Euro 2012 is the priority. I'm totally focused on the national team."
The 23-year-old scored Poland's goal in the first half, only to see Greek substitute Dimitris Salpigidis equalise after the break in a match which saw both teams finish the game with 10 men.
But he rued a string of missed Poland chances which could cost his side in Group A, especially missing a first-half header in front of a gaping goal.
He said: "I did everything to take the ball. I was just millimetres away but this is football and I hope next time I score.
"I regret that we did not take more of our chances in the first half. It could have been two or three zero but we still have a positive attitude."