I recently got a ultrasound done on my thyroid after experiencing moths of pain in my throat. It started on my right side, and the pain slowing migrated to my left. My doctor told me they found several cysts, and one of them was
Cysts (that is fluid filled) on the thyroid are rarely cancerous. If you have a solid or cystic thyroid nodule around 1cm, you will need a needle biopsy. Nodules are common, 95% are benign, and they just happen.
I doubt you have to worry, but thyroid cancer is rare, and it's actually curable....so don't worry---and they can't tell anything at all in terms of malignancy from an ultrasound.