The world faces a "nuclear crisis" from a "bruised ego", the International Campaign to Abolish Nuclear Weapons (Ican) has warned in an apparent reference to US-North Korea tensions.
Accepting the Nobel Peace Prize on Sunday, Ican's executive director Beatrice Fihn said "the deaths of millions may be one tiny tantrum away".
"We have a choice, the end of nuclear weapons or the end of us," she added.
Tensions over North Korea's weapons programme have risen in recent months.
The open hostility between US President Donald Trump and the North Korean leadership under Kim Jong-un has at times descended into personal attacks this year.
Speaking at the ceremony in Oslo, Ms Fihn said "a moment of panic" could lead to the "destruction of cities and the deaths of millions of civilians" from nuclear weapons.
The risk of such weapons being used, she added, was "greater today than during the Cold War".
Ican, a coalition of hundreds of non-governmental organisations (NGOs), has worked for a treaty to ban the weapons.
Prior to presenting the prize on Sunday, Nobel committee chair Berit Reiss-Andersen offered a similar warning, saying that "irresponsible leaders can come to power in any nuclear state".
Ms Reiss-Andersen commended Ican which, she said, had succeeded in highlighting the dangers of nuclear weapons as well as trying to eradicate them.
Ms Reiss-Andersen also acknowledged the contributions of Setsuko Thurlow, an 85-year-old survivor of the Hiroshima atomic bombing and now an Ican campaigner.
Ms Thurlow, who was rescued from the rubble of a collapsed building at the time, said that most of her classmates, who were in the same room, were burned alive.
"Processions of ghostly figures shuffled by," she said on Sunday. "Grotesquely wounded people, they were bleeding, burnt, blackened and swollen."
North Korea and Trump
Mr Trump has warned that North Korea's government will be "utterly destroyed" if war breaks out.
White House national security adviser HR McMaster said last week that the potential for war with North Korea was increasing every day.
In November, Pyongyang said it had tested a missile capable of carrying a nuclear warhead and reaching the whole of continental United States.
Ican, formed in 2007 and inspired by a similar campaign to ban the use of landmines, has made it its mission to highlight the humanitarian risk of nuclear weapons.
A coalition of hundreds of non-governmental organisations (NGOs), the Geneva-based group helped pave the way for the introduction of a UN treaty banning the weapons, which was signed this year.
While 122 countries backed the treaty in July, the talks were notably boycotted by the world's nine known nuclear powers and the only Nato member to discuss it, the Netherlands, voted against.
Only three countries, the Holy See, Guyana and Thailand, have so far ratified the treaty, which requires 50 ratifications to come into force.