Weird looking mole

Warning: my English is not that great!

A couple years ago i developed a mole on my arm. At first i didnt think much about it, but as soon as the mole became darker i started to worry. Got it checked out, but my doctor said it was nothing. I dont sunbath

Well, this (picture) is the mole now. Without any reason it became a small wound. My boyfriend said not to worry, but i’m pretty worried. I’m also going to call my doctor about it.

Is every mole that does this cancerous?