Lithium is well known to cause goiter and thyroid function problems -- most commonly hypothyroidism, but sometimes hyperthyroidism. It is also well known to trap iodine -- making the uptake value slightly high, but not alarmingly so. Lithium is not known to cause nodules, so if the ultrasound shows nodules, then that is not likely related and biopsy may be indicated.
If lithium is causing a problem, the TSH is usually elevated -- would look closely at the TSH value and if it is borderline high, in the presence of a goiter, would consider thyroid hormone treatment. The goiter may happen even with preserved thyroid function.
TK
With what you've just described, you definitely need to be seen by an endocrinologist for reevaluation and management.
Best wishes
Sally