"The doctors consider it appropriate to intervene and so, following their advice, I decided to have surgery to remove it," he continued. "The surgery is already scheduled for the next few days. I thank you for your spiritual closeness and I rely on your prayer."
The surgery is likely to take place within a few days at the Gemelli Hospital in Rome, which is known as the "Pope's" hospital, Vatican sources told Fox News.
The Vatican has not disclosed whether the nodule is cancerous, and no further details about the pope's diagnosis or the planned procedure were immediately available.
The announcement comes as a surprise for the American-born pontiff, who has no previously known health problems and is known for maintaining an active lifestyle.
Leo regularly plays tennis and swims at the papal summer retreat in Castel Gandolfo, according to The Associated Press.
The pope is also scheduled to embark on a major international trip from Nov. 6–17, with planned stops in Uruguay, Argentina and Peru. It remains unclear whether his surgery and recovery will affect those travel plans.
In addition to addressing his health, Leo used his Sunday remarks to renew his appeal for peace in war-torn Ukraine, warning that the conflict continues to inflict suffering far beyond the country's borders.
"The war in the martyred Ukraine continues to create suffering, even beyond its borders, especially in the poorest countries, where many people depend on the exports of cereals and grains," the pope said.
Fox News' Courtney Walsh and Stephen Sorace contributed to this report.