I had a thyroid ultrasound and the findings indicated that the thyroid gland is borderline small. impression, small, heterogeneous what does this mean?

Check with your doc: Usually means nothing. Ask your doc about thyroid function testing.

Thyroiditis: This is a nonspecific findings. It, however, typically suggests sequelae of a prior inflammation of the thyroid gland, such as hashimoto thyroiditis. After the acute inflammation, the thyroid gland becomes fibrosed and scarred and shrinks in size. What's more important is your thyroid function tests and that there were no report of any thyroid nodule to biopsy.