The Pretty Little Liars star was practising a routine with professional dancer Valentin Chmerkovskiy when she felt a pang in her chest and could not continue.
In footage obtained by Tmz.com, Parrish undergoes a scan and a massage while lying on an operating table and is told her injury appears to be a compressed rib.
Parrish sobs as she tells Chmerkovskiy, "I felt it and I was like, 'Oh I can dance through it' and then I literally had to stop moving. I'm just worried. I'm freaking out a little bit."
The actress is set to compete against Fresh Prince of Bel Air actor Alfonso Ribeiro and reality Tv star Sadie Robertson in the final, which airs in the U.S. on Tuesday night (25Nov14).