cancer is pretty treatable in this case and rarely does it spread.
Some are palpable when small, others are not when big. It depends on where they are...closer to the skin they can be felt, but if they are on the interior side of the thyroid or near the trachea, they may not be felt until they are big. I had four, largest one was 2.1 cm, it couldn't be felt, but the 1.6 cm one could...one was in the left, the other in the right.