I noticed on my gum behind my molar a very small black or dark blue round very small spot almost like the size of a pinhead it does not hurt ?

Have to see: What you describe could be from trauma. The trauma does not have to be severe, but I have seen those spots from biting on a pencil, chewing food that caused a small bruise or it could be from an inflammation from the tooth in front of the area. You should see an oral and maxillofacial surgeon if the area does not resolve within a month.

Spot: Probably a tiny black and blue mark from trauma. May be a ruptured capillary. May be a blue nevus. May be an amalgamtatoo from an old silver filling. So may possibilities. If it doesn't spontaneously disappear within 1014, days, see an Oral Surgeon.