Since I have hypoechoic mass on left lobe thryoid and already had total parathyroidectomy, can this be cancer?

Thyroid nodules. Many people have thyroid nodules. Most are benign. There are many features that a radiologist will look for in thyroid nodules to help determine if further evaluation is needed. The most important features are calcification, taller than wide nodules and irregular microlobulations. If need be a fna or core biopsy can be preformed. If this is a solitary nodule and depending on your age a simple biopsy could be performed.
May need follow up. The data says that without a dominant mass, nodules less than 2.5 cm are rarely of concern. The thyroid frequently forms nodules, most of which are of no concern. If the nodule is worrisome on ultrasound, then a thyroid nuclear medicine scan or biopsy would be indicated.