VP of medical services Stan Conte and Mattingly looked at Nicasio's middle finger on his right hand after he issued a walk to David Peralta with one out in the sixth inning.
Nicasio entered the game at the beginning of the inning with the Dodgers holding a 5-4 lead and faced three hitters, throwing 14 pitches.
Nicasio earned a start in the first game of a day-night doubleheader against Colorado on June 2 and only threw two innings. He said the nail cracked then and he has been dealing with the injury for the past week.
"The last three games it's bothered me a little bit," Nicasio said. "Hopefully once we go to San Diego [on Friday], I think it'll be OK."
Steve Bourbon is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.