A cold nodule is composed of cells that do not produce thyroid hormones (don't absorb iodine). Hot nodules produce too much hormones.
"85% of thyroid nodules are cold, 10% are warm, and 5% are hot. Remember that 85% of cold nodules are benign, 90% of warm nodules are benign, and 95% of hot nodules are benign."
http://www.endocrineweb.com/conditions/thyroid/fine-needle-biopsy-thyroid-nodules
You can see that approximately 95% of all thyroid nodules are benign (non-cancerous).