You've been given some good advice... Thyroid nodules, if that's what you have, are very common with, both Graves Disease and Hashimoto's... I, personally, have quite a few of them. Less than 5% of all thyroid nodules turn out to be cancer.
What blood test did they do? Was it for thyroid? Do you have the results? Is so, please post them, along with reference ranges, which vary lab to lab and have to come from your own reports...
First of all worrying doesn't help anything. It just takes your peace away for today. It is not uncommon to have nodules. You cannot know anything without a Fine needle aspiration biopsy. Also called FNA. Just calm down and wait for the results of your tests. If it turns out to be malignant then you'll do fine with a thyroidectomy. Cross each bridge as you come to them. No point in trying to jump hurdles that are only imagined. You are going to stress yourself out. Back pain can come from thyroid issues and a lot of other things too, like stress. Pray and keep calm.
For thyroid MRI is not as accurate as ultrasound; the areas of inflammation may look like nodules on MRI. if you post the report it will be possible to give better answer