What Does A Round Mass On The Anterior Side Of Neck Indicate?

I have a single regular rounded mass on the anterior side of my neck on thyroid ( incidental finding in ultrasound school). It is only 0.5 x 0.5 cm. The Doc (informally) told me that it is nothing to worry about, like having a freckle, but I am very worried it may me more serious. I do not have insurance so rushing to doctors is not an option. Is it something that needs to be watched - I heard they do biopsies only if the mass is 1cm or more...