What Causes Dark Red Spots In Skin?

Hi- I noticed a few months ago a small group of dark red spots, then a few weeks later they were raised and had a scan like texture. When I scratched them they came off like blackheads but hard like little seeds. They faded but left a bit of a scar where the spots were. I just noticed a new set of thre in a line started out red and flat but have developed the same way. Should I be concerned?they are not painful or itchy.