Small dark lump under skin
I'm 23 and have not spent too much time in the sun. About a week ago I noticed a small, dark lump UNDER my skin. It's about 4-5 inches below my arm pit, and a few mm in width. It's round/oval in shape, and hard. It's not particularly painful, even when squeezed. It's approximately the color of a blood blister. There's a white line on it.
However, I think the site may be the location of what was formerly a white lump that I never thought much of, and my doctor had never commented on. But I'm not entirely sure if this is the same spot.
Right now I'm on vacation until the end of September, a few hours from my doctor. I called the only local dermatologist yesterday and I couldn't get an appointment until December. Of course, skin cancer seems extremely unlikely given my age, how much sun I've gotten, and how much sun this spot specifically would have received. I've also scanned the Internet for images of cancer that look anything like this, but nothing matches the color (purple/navy blue) or the regularity of the shape.
I'm curious if anyone has any idea what this might be. I'm planning, on Monday morning, to see a Dr about this...