Hello.
On my chest, I have three tiny pinholes in my skin that fill up with dirt. I know its dirt because I can squeeze the hole and black stuff comes out. It's like a crater, but the size of a pin head. Is that cancerous? They are located around where my bra under strap hits. Also used to have one on the back of music heal but I cut it out. It came back a few times, but finally went away....