updated 01/06/2012 AT 2:00 PM ET
•originally published 01/06/2012 AT 3:00 PM ET
When Michelle Williams took a holiday vacation to Mexico, she may have gotten a little more than she bargained for.
“I’m still a little sore,” she told Jay Leno on Thursday’s episode of The Tonight Show when asked about her trip.
The My Week with Marilyn star was vacationing with a group of friends when they decided to try horseback riding.