There's nothing wrong with honey that has turned cloudy and become thick.
To return crystallized honey to liquid form, place honey container in hot water for 5-7 minutes. Be careful of how hot you get the water; it can destroy some of honey's natural antioxidants. Do not heat honey in the microwave because it alters the honey taste.
It only takes a few minutes for honey to turn back into its original liquid form so every couple of minutes pull it out of the water to see if it's liquified.