Lumps/divots in head possibly since birth. What are they, trouble?

I've had these two "holes" in my head, possibly since birth. My mom tells me they're from having needles in my head as a baby; I was premature and stayed in an incubator for three months.
For a while now, there has been a firm swelling around these holes, a bit firmer than the cartilage of your nose. Hair grows from these holes and lumps, but the hair grows out scraggly (I otherwise have very straight hair). I can't look at it directly because it's on the top-left back of my head. I would guess that it takes up a 3/4 of a square inch. I actually hadn't noticed the second hole until I was a teenager because that area had always been pretty flat, but I pointed it out to my mom, and she said that there'd always been two.
When I was younger, I think one of the holes bled sometimes because I would touch it and find a small scab at the center. Neither bleed at all anymore. But the swelling/lumps have gotten larger, to the size I mentioned. When I was younger the area was flat enough with just the slight indentation where the holes are.
Oh, and it's probably worth it to mention that I was born in 1990 in South Korea, if that makes a difference.

It's difficult to communicate with my mom because English is my primary language and her second, and she's very opposed to being asked questions.

Has anyone heard of anything like these holes/lumps before? I know they're probably not going to give me any problems outside of the vanity issue. But I would like to know what exactly caused them; what they are; would it be advisable to get rid of them?