Pope Francis suffered a black eye after hitting his head on the so-called Popemobile when his vehicle stopped suddenly.
The pontiff was met by hundreds of well-wishers in Cartagena, Colombia, on the last day of his visit to the south American country.
He lost his balance when his motorcade came to an abrupt halt, bruising his left eye and cutting his left eyebrow which dripped blood onto his white cassock.
The cut was swiftly treated with ice and bandaged up.
After the morning's dramas, the 80-year-old prayed at the tomb of St. Peter Claver, the 17th century missionary who ministered to hundreds of thousands of African slaves who were brought to be sold through Cartagena's port during Spanish colonial times.
Francis, known for his own simple and austere style, said Claver was "austere and charitable to the point of heroism."
Claver, the self-described "slave of the slaves forever," has been revered by Jesuits, popes and human rights campaigners for centuries for having insisted on recognising the inherent dignity of slaves, treating them as children of God when others considered them mere merchandise to be bought and sold.
Francis said the legacy of the Spanish priest should serve as a model for the Catholic Church today to "promote the dignity of all our brothers and sisters, particularly the poor and the excluded of society, those who are abandoned, immigrants and those who suffer violence and human trafficking".
And he cited Claver's courageous and controversial example in urging Colombians to take a brave first step to reconcile with one another after a half-century of armed conflict.
"Colombia, your brothers and sisters need you. Go out to meet them. Bring them the embrace of peace, free of all violence.
"Be slaves of peace forever," he said in an appeal at the end of Mass in Cartagena's port.
It was a final appeal to Colombians to overcome divisions that linger after the government reached a peace deal with leftist rebels hoping to end Latin America's longest-running armed rebellion last year.
Francis travelled to Colombia to help solidify the deal and encourage Colombians to reconcile.
For the second day in a row, Francis also made an off-the-cuff denunciation of drug dealers and traffickers, condemning them as unscrupulous merchants of death who "cut short so many hopes and destroy so many families".
"You can't play with the lives of our brothers or manipulate their dignity," he said.
Francis had refrained until Sunday from speaking out about the political and humanitarian crisis next door in Venezuela.
But in remarks added into his Sunday prayer, Francis called for an end to political violence in the country and protection for the poor who have been most hurt by the crisis.
While the appeal was welcomed, many in the crowd were more taken by Francis' mishap on the popemobile and his bruised and bloody eye.
"This holy blood is staying in Colombia," said Ricardo Morales, a lawyer who lined up outside St. Peter Claver's church for a glimpse of the pope. "He made a great effort to be here and from now on it's our obligation to make a similar effort to thank him for everything he has done."