While Marvin Martinez found the ticket in 2012, he only learned recently he could benefit from it, the New York Post reported.
The New York State Gaming Commission said there is a one-year waiting period for found tickets to give owners a chance to claim them.
"This was someone else's luck, but my ticket," Martinez told the Post.
He said Friday he had forgotten about the ticket when he received a call from lottery officials three weeks ago.
Martinez, 27, lives in Hicksville on Long Island with his mother. He found the ticket in Bayville while working with a colleague picking up leaves.
The ticket was a "Win $1,000 a Week for Life" scratch card, but Martinez elected the cash option. That gives him $515,612 after taxes.
Martinez, who recently married, said he plans to buy a house and use some of the money to help relatives in El Salvador.
"This won't change the way I live my life," he said. "I'm still going to keep working six days a week."