As he explained to MLB Network after the game, he hurt his shoulder with his Bash Brothers-type celebration with teammate Kike Hernandez (1:30):
"I'm good," Bellinger explained. "I hit Kike's shoulder a little too hard, and my shoulder popped out, so I had to go back in the training room. They popped it back in, and I was ready to play some defense. It kinda hurt."
The moment in question came in the seventh inning of Game 7 of the NLCS, with the Dodgers and Atlanta Braves tied 3-3. Bellinger hit a no-doubter home run, putting Los Angeles ahead for good in the 4-3 win.
After rounding the bases, he had an aggressive jump with Hernandez (:33):
Though he appeared to be favoring the arm during the next inning, he remained in the game as Los Angeles clinched the NL pennant for the third time in four years.