Without being able to see it, from your description it sounds very benign and most likely what is called a labial melanotic macule.
These are like freckles.
They are more common in women over the age of 40..however they can occur in men and at any age.
As you may know with melanoma, the most important signs to look for are the ABCD's
Asymmetry (one half is different than the other half)
Border (irregular border, hazy border)
Color (different colors within--black/brown)
Diameter (larger than a pencil eraser)
I would have your doctor look at it because it is new..but you are not describing anything worrisome at this time.
Here is a link to read about labial melanotic macules:http://www.skinsight.com/adult/oralMelanoticMacule.htm
Feel free to ask any follow up questions you may have,
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