I don't know of any relationship between smoking and thyroid disease, but quitting smoking is by far the best thing you could do for yourself. I quit 15 years ago, and I am eternally grateful for many reasons. Please do move forward with that; the longer you wait the harder it is and the more likely you will have permanent damage.
We all know smoking causes lung cancer, heart disease and strokes. But did you know it can also cause you to lose your teeth from periodontal disease? That it changes the chemistry of your skin and causes your face to age prematurely?