It is common for swelling around the eyes following a head injury
as the peri-orbital region is made of spongy tissue which can retain fluid more than other areas. I don't think it should be a matter of worry and you can certainly wait for the swelling to subside gradually over 1-2 weeks. The dark circles
are due to breakdown of the blood products and can have a purplish or greenish hue. It will disappear gradually over the next few days.