Malachowski wrote, according to Facebook's translation: "In Rio I fought for gold," "Today, I appeal to everyone -- let's fight together about something that is even more precious. The health of this fantastic boy."
According to Malachowski, the procedure to treat the rare form of cancer isn't available in Poland; it is offered only in New York.
Malachowski said on Facebook that siblings Dominika and Sebastian Kulczyk,who are among the richest Poles, "declared the intention to buy my silver medal," which he put up for auction to help pay for treatment of the boy, Olek, who is suffering from retinoblastoma.
Malachowski did not reveal the amount he raised by selling his medal on Friday, but said the target, which was almost $130,000, has been met.
"My silver medal is worth much more today than it was a week ago," Malachowski said