Hypothyroidism ultrasound shows hypervascular solid nodule inferior left lobe. 13x9x10mm. what is the next step? odds of being malignant?

Thyroid nodule: A solid hypervascular nodule should probably be biopsied, unless it is a hyperfunctioning (prob not since you're hypothyroid). If it is a "cold" nodule, the odds of it being malignant is less than 20%, but most thyroid cancers are slow growing and very treatable. All of this is relatively complicated, and you should be seeing an Endocrinologist who does thyroid ultrasound and biopsies.

FNA biopsy: Hi. The nodule could be cancer (although considering all nodules, odds are in your favor it's not). Make sure TSH is not suppressed (if it is, you need a thyroid scan...hyperfunctioning nodules are never cancer). If TSH isn't suppressed, you need a fine needle aspiration biopsy for cytology (and hopefully gene testing). Good luck!