The most common complication from having blood drawn is bruising at the puncture site. Care should be taken to assure bleeding has stopped prior to leaving the lab area. If you experience slight bruising, an ice pack, applied briefly to the site, may relieve the discomfort.
Bruises, or ecchymoses, are a discoloration and tenderness of the skin or mucous membranes due to the leakage of blood from an injured blood vessel into the tissues.
The blood under the skin which causes the discoloration of bruising should be totally reabsorbed by the body in three weeks or less. At that time, the skin color should completely return to normal.
Sometimes, a bruise may become solid and increase in size instead of dissolving. This may indicate blood
trapped in the tissues, which may be need to be drained. This is referred to as a hematoma. Less commonly, the body may develop calcium deposits at the injury site in a process called heterotopic ossification.

http://www.healthline.com/adamcontent/bruise

really painful! having blood taken sucks. they tried to do it to me today, twice, but my veins are rubbish! they bruised me though. and it hurt.

I would call it a haematoma

it's very common..
it's just because your skin is very sensitive and it's not used to needles and such things..
so don't worry.

It's a boo-boo. :-)

puncture site..Ü