Thyroid nodules are very common. The least concerning nodules are cystic nodules, as in your case. The most concerning nodules are solid nodules, especially those with microcalcifications, which are suspicious.
Because thyroid nodules are exceedingly common, leading to costly interventions for many lesions that ultimately prove benign, the American College of Radiology developed a standardized scoring system called TI-RADS:
I too had a walnut size nodule in my thyroid. They said my functions were normal. Not! Had surgery to remove that half. Turns out that I had another behind it. It was my parathyroids that we’re the problem. One grew into my thyroid (walnut size) and the one ENT saw was behind that one. I had to have another surgery which resulted in losing all my parathyroids. (4) My blood calcium level was 170 should had hAve been 9-11. After surgery it dropped to 3 and I was hospitalized because of cramping thruout my body. Your kidneys are the only way to rid the body of excess calcium. My kidneys failed and I was on dialysis for 6 weeks before these surgeries. Keep an eye on your PTH (9-11) GFR (60 or above) and creatine (1.0 to 1.5). My kidneys are now functioning at about those numbers now. A little low on GFR and PTH IS LOW but I take Calcitriol 2 grains a day. You can’t live without them. OTC calcium is not blood calcium. Hope you get better.