"I really overworked the right side of my back in this dance all week," the double amputee Paralympic snowboarder, 34, told PEOPLE on Tuesday, following a night of receiving emergency treatment. "The hospital took X-rays and everything looks good, but a rib is out of place and the muscles are in spasm."
Purdy says the rumba was a challenging dance because the movements required her to hold her shoulders down and use her right side for stability and twisting.
"I was sore yesterday morning and got a massage before the show and felt better," said Purdy, whose performance with Hough went off without a hitch. It wasn't until the duo was "walking away from the judging table" that "I turned my head and my upper back popped, which put my muscles on the right side in spasm. I barely made it through scoring without passing out."
Now recuperating at home, Purdy says she's "being very proactive, icing all day, taking anti-inflammatories and working with a sports doctor to try to heal quickly so I can learn this week's dances."
Purdy, one of five celebrities left in the season 18 competition, will know on Wednesday if she'll be able to resume rehearsals and participate in next Monday's show.