The former South African president's "Hand of Africa" piece was said to have been created by accident while working on a sketch inspired by his 27-year imprisonment on Robben Island.
Anna Hunter, the owner of the Belgravia Gallery, where the paintings are displayed, said at the launch: "He got his hands dirty when he was producing 'The Lighthouse' and he wiped his hands on a piece of card."
"You can see the image of Africa in the palm of his hand."
Hand analyst Lori Read was quoted by The Times newspaper as saying it was very interesting in a symbolic way.
"It is almost as if the continent is imprinted on his soul."
The other image of Mr. Mandela's on display is a handprint of his, surrounded by the smaller handprints of HIV-positive children.
Mr. Mandela has received some teaching from a professional artist and has done some colorful impressions of his prison.