Nodular Melanoma Concerns

The internet is full of varied descriptions on what Nodular Melanoma looks like, but it seems like the majority of cases are jet black?   Some sources say it can be light brown, to dark brown too which would pretty much fall under the same category as an ordinary mole.

Is there anything that nodular melanoma does that is blatantly obvious and sets it apart from a regular mole?  How would someone know they even have it to catch it early enough?  Soreness, ulceration and bleeding would be fairly obvious, but again it sounds like that isn't always the case with nodular melanoma.

As far as nodular melanoma not having any radial growth, does this mean that it could be the size of a pinhead and basically continue growing downward, once again making it impossible for someone to catch it?  Or does nodular melanoma generally grow fast, and grow outward to that point that it sticks out further than most moles?

The reason I ask all of this is because about 1-2 years ago I noticed a mole on my collar bone.  It is raised, quite a bit smaller than an eraser, and very symmetrical.

We use wood heat in our house, so it is extremely dry and my skin suffers in the process.  The mole at the time was pretty dry itself, and I assumed that was just the result of the dry air.  It hasn't grown since then, radially or outwardly but recently either due to some sun exposure from being outside, or possibly from irritation from my t-shirt collar because I run 7 miles a day, the center part of the mole has taken on a darker tint.  By dark I don't mean black, but just a darker brown compared to the rest of the mole which is a light brown.

I've had my body checked and moles removed this year by my GP, but this one was passed over.  The mole bothers me for two reasons:

1.)  1-2 years ago when I first noticed this mole, I didn't really remember it being there.  That doesn't mean it wasn't there, but I'm not certain.

2.)  The color change, and that it gets dry and rough so easily.  If I lotion it up it will stay soft for a few days, but I have to wonder if there is something more to this than just dry skin.

I guess nodular melanoma would have been pretty obvious by now since it has been there for quite some time, but is there a possiblity that I could be wrong in that assumption?

(I am visiting my GP for a tetanus booster tomorrow and plan on bringing up the mole; I'm also planning on taking a picture of it and posting an official question to a doctor here.  I just really want to know what the community has to say, and perhaps it could ease my mind a bit)