It's true that thyroid cancer is relatively rare. Less than 5% of all nodules turn out to be cancerous.
There's a system of scoring thyroid nodules, called "TI-RADS". Without more information, I can only assume your doctor is saying that your nodule is a TI-RAD 3 on a scale of 1-5.
A TI-RAD 3, typically means the nodule is "probably" benign (< 5% chance of being cancer). That means it has a score of zero. Often a "wait and watch" approach is taken with this type of nodule.
It's only when the nodule reaches TI-RAD 4 that they get into sub-categories, a, b, and c.
If you can get a copy of the actual biopsy report and post it here, that would be very helpful as then we'd be able to see exactly what your doctor was referring to. If you're in the U.S., you're entitled to a copy of the report if you ask for it.