The 23-year-old had to be stretchered off the pitch after a challenge by County midfielder Tom Miller.
The Korean international underwent successful surgery after tests revealed that he had a double fracture of his right leg.
"We will make sure Chung-Yong gets all the support he needs," manager Owen Coyle told the club's official website.
"Now it is all about his recovery and his well-being, that is the most important thing. The operation went well and we would like to pass on our thanks to the medical staff involved."
Lee signed for the Trotters from FC Seoul in 2009 for £2.2m.