Thyroid is moderately enlarged (about 1.5-2x normal). My guess is the "nodule" is an area of marked inflammation from hashimotos, but the only way to document that is a biopsy -- would go ahead with this -- must be under ultrasound guidance.
What I understand from what I have read, all lumps or nodules in the thyroid gland have to be investigated one way or another. Nodules are biopsied if they show active growth or are unusually large, hoarseness and/or change of voice, etc. and helps determine which kind of nodule you have. Thyroid Needle Biopsy has become the most reliable test and provides information that no other thyroid test will provide, and, it will provide definitive information in 75% of the nodules biopsied. Better to be safe with test done now than to be sorry later.
Just to add one more thing...don't work yourself up over the biopsy (as far as the procedure goes). I did and it ended up being so not worth all the worry and anxiety I gave it...so if you need it done, please don't do what I did to myself (if you can help it). Just my two cents!