L have been diagonised as having a non-toxic thyroid, but i see a not so noticeable slight swell in front of my neck area, how can l stop this.

Ignore it: If you can't ignore it, thyroid replacement with brand name T4 may make it decrease in size or at least not enlarge further, but then you're taking a medication life-long for a non health- or life-threatening problem. Talk w/your doctor.

Swelling: The slight swell that you are noticing may not even be your thyroid. There are lots of structures in the neck. Ask your doctor to describe where your thyroid is, and try not to obsess about the slight swelling.