Have it replaced under warranty. If it wasn't under warranty, you can remove the bulb, take a hairdryer on low heat and dry it all out. The back of the light has breathers that are supposed to keep it from fogging up, if those are blocked with mud they can't breathe.
2013 JKU Sport, billet, auto, 3.73, LSD, 315/75/16 Duratracs on MB 72, 10A springs, Bushwacker flatties
Sold - 2005 TJ, red, auto, 3.73, 33" Duratracs, 4" lift
Ice storm casualty in 2007 - 2003 TJ, green, auto, 3.73, 33" Duratracs, 4" lift