Suggest Treatment For A Melanoma Like Spot On Arm

I have a mole that I have had for as long as I can remember on my upper right arm. In the past it has always been a light brown color about the size of an eraser on a pencil and more oval shaped in nature. I have recently started inspecting my moles when getting baths/showers as I have many moles on my trunk area especially. Last night I noticed that a black area was on top of it that almost looks like a little blood blister (it is smaller than my original mole but nonetheless formed on top of it). Could this be the beginnings of melanoma or more likely to be a blood blister or irritated mole? It does not itch nor is it that painful. It has bled just a little bit when I was in the bath tub. No immediate family members with melanoma but do have many irregular moles. 33 yr old female....Thank you....