The 27-year-old was put on the transfer list in the summer and has not played for the Whites since the draw at Cardiff at the end of last season.
Nunez, who was on contract at Elland Road until 2015, joined from Honduran side Deportiva Olim in August 2010 under Simon Grayson.
In all, Nunez has made 25 appearances in all competitions, scoring five goals.