Your doctor has advised you correctly as the recent ultrasound
suggests growth in the size of the nodule. So the FNAC- fine needle aspiration cytology is recommended, not a biopsy
directly. Please clarify this from your doctor. The FNAC procedure involves hardly any risk if done by an experienced pathologist as the thyroid
gland is a gland situated just under your skin and the needle does not penetrate your vital structures of the neck. The risk of increasing size of solitary (lonely) nodule is that it can be malignant and if not evaluated for malignancy early then the spread of malignancy to other tissues would happen, though thyroid cancers are very effectively treated and they spread very slowly. But to be on safer side, please get the FNAC test done. Take care.