Those look very much like simple bruises in the healing phase.
Some bruises appear to be blue or reddish or purple when you get them.
Some more minor bruises can have this appearance
I would expect these to be gone in a few days.
They are a bit sore, so that would explain it. But I don't remember getting hurt in that area. However, I did receive some shots in that area. Could that explain it?
yes. the shots could explain it for sure. and sometimes we bruise from minor bumps without noticing that they were particularly painful.