"I just was taking swings in the cage and felt a sharp pain," Beltran said. "I took another one and felt the same, and told [manager] Joe [Girardi] that I wasn't going to be able to continue."
Beltran had an MRI exam performed on Monday and said that he was told the bone spur has been there for a while, but he was not aware of it until now. Even if the cortisone shot permits Beltran to continue playing, he said that he may have surgery this offseason to shave it down.
"I think you have to give the cortisone shot a chance to work," Girardi said. "They believe it's an old bone spur. It's aggravating his elbow now. If in a couple of days he doesn't feel better, then my level of concern would be pretty high."
Beltran, 37, is in the first season of a three-year, $45 million contract with the Yankees. In 33 games, the veteran is batting .234 with five home runs, 15 RBIs and a .715 on-base plus slugging percentage.
Girardi said that the Yankees will wait two or three days to see how the situation plays out, and they will not place Beltran on the disabled list until they have more information.
"Right now, I'm day to day," Beltran said. "Let's hope tomorrow the injection does the job and I'm able to come here and do the work that I do."
Bryan Hoch is a reporter for MLB.com. Follow him on Twitter @bryanhoch and read his MLBlog, Bombers Beat. This story was not subject to the approval of Major League Baseball or its clubs.