Hello,
I am really sorry to hear about your news and hope that you have made a good recovery following your operation. As a doctor, and aspiring pilot, but not an AME, I hope I can give you some insight. There are several issues with this.
1. You will need to have normal thyroid function to fly. As you have had (I am assuming a total) thyroidectomy, with Radio-iodine ablation you will require thyroxine replacement therapy. It may take some time before your thyroid function is biochemically normal. There are some who advocate a slightly "supra-therapeutic" dose of thyroxine in order to supress Thyroid stimulating hormone and therefore thyroid growth.
2. Further ablation or surgery may be required in the future. Occasionally radiotherapy is required if ablation has not been 100% effective. Follow-up imaging is required in all cases.
3. You may be required to demonstrate normal calcium levels due to the potential for damage to the parathyroid glands during thyroid surgery.
Prognosis is very much dependent upon the histology of the tumour, and the most common types of thyroid carcinoma are associated with very good prognosis and response to treatment.
Not being an AME, I cannot be absolutely sure about the procedures required, but from a purely medical point of view these are the issues I would anticipate.
Wishing you a full and speedy recovery.