I had one on me 7 years ago and I've done radioactive test to see if there's single or more and wether solid or not. I think you should done that too. My opinion is, if it is solid nodule its better if you remove it asap, it's like you dont want to have time-bomb inside, cause if the lab says it's ok at the moment, who knows 1 or 2 yrs ahead.
How have you discovered the nodule ( visible swelling; self test, etc)?
Is it the hard lump that moves up while you swallow?
The best way to verify the presence shape and type of the nodule is the ultrasound.
I agree with redheadaussie, Ultrasound is a good start, and then if needed they can go onto other types of testing. I've just had one done for a lump, and it basically told me most of what I needed to know, and that other testing may be necessary as a result.
A goiter is the thyroid enlarged by disease or excess thyroid hormones. Lump/nodule is on or in the thyroid itself. Many people have lumpy bumpy thyroids and never have known it or have any problems at all. A goiter on the other hand can get very painful in pressure and stick out of your neck in a big way. You can have a lump anywhere on the thyroid and even just on one side.
Ultrasound is one of the recommended ways of seeing what is going on. Usually this is very good and can show any lumps quite clearly. If not then an MRI or CAT scan is done. If it looks ok the lump may be left alone to monitor for a while. If it looks suspicious a biopsy is usually taken. (Not always at the first ultrasound test) If after that the lump is deemed a bad guy, then there are options, medication or surgery depending on the type it turns out to be.
Right now it seems you are concerned with a single lump on a thyroid. First step is the ultrasound and see what happens from there. More often than not there is no problem, but you won't see that on the forum as most of us have had something wrong.
Hope that helps!