Possible Skin Cancer on Freckle

I have pretty fair skin and have always had my fair share of freckles.  When I was a child and teenager, I never wore sunscreen and ended up with a few nasty burns on my shoulders.  Some of those burns included countless blisters.  To say the least, I was in agony and a bit grossed out.  Now both of my shoulders are pretty much covered in freckles.  Most of them are small, normal freckles.  However, there are several that are darker, very smooth and somewhat larger.  These darker freckles also are somewhat sunken in.  It is not noticeble.  I only saw this when inspecting my shoulders after seeing a tiny black place on the biggest and darkest of those freckles, but I'll get to that in a second.  They are just barely, barely sunken in.  You could not see it unless you had perfect vision and were right upon them.  From some research, I believe that these are "sunburn freckles."  I was just wondering if it was normal for them to be slightly sunken below the skin from sun damage?  Now, to the pertinant issue.  Like I said before, on the biggest, darkest "sunburn freckle," there is a teeny, tiny black spot.  The width is the size of, if not smaller, than the point of a needle.  And it is no so much a spot, as a line.  The length is around 2 to 3 mm.  It is extremely tiny.  It appears to be very dark brown or black.  Because of it's color, I'm convinced it's skin cancer.  At first, I thought it was a blackhead because I'm no stranger to acne, but it obviously wouldn't pop.  I noticed it around 3 or 4 months ago and it has not gotten bigger or changed whatsoever.  I'm calling to get an appointment with a derm this morning ASAP.  I would just like some opinions while I wait.  Thanks so much!