Blue dot on gums

Hi.
I recently found a blue dot above my teeth, close to the line. It appeared recently. The dot is regular shape. I had a lot of dental work.The dot is not close to any tooth worked on recently, but as I said, I had a lot of work (I put my dentist's kid through a private school :).
and practically every tooth altered/fixed in a way. I also have a crowns made 3 years ago. They are supposedly to be gold underneath, but I doubt.
My dentist took an X-ray, and couldn't see anything. It is soft. He is not worried, and said It is a superficial, and pigmentation, the most possibly silver/amalgam tatoo/pigmentation. He advice me me to watch If it grows.
I am a female, 36 years old, non smoker, not a drinker, vegetarian, slightly overweight.
No history of cancer in the family.
I think I want to have a biopsy performed, and remove the dot, because It freaks me out.
Any advices/ideas?

Thank You!