"A comprehensive test was carried out on the player Monday and the doctors said Ambrose can continue his football career," Nigeria Football Association (NFA) official Mohammed Sanusi said.
"The doctors in Korea told us that the player is fit to play as his heart condition is consistent with that of other athletes and as such there is no cause for concern.
"The player has since resumed training with the rest of the team. He is relieved he can now fight for a place in the Olympics team."
Ambrose, who featured at last year's FIFA U-20 World Cup in Canada, feared losing his place after he was diagnosed with a heart condition in Nigeria before the team left on a tour of Korea ahead of the Olympics.
In the meantime, officials also confirmed that goalkeeper Vincent Enyeama, one of the three over-aged players picked, will not be available after his Israeli club Hapoel Tel Aviv refused to release him.
But another over-aged player, Getafe striker Ikechuku Uche, will compete.
Nigeria are drawn in a first round group that also includes the Netherlands, Japan and the United States.