Pain in the arm after a blood draw is relatively common. In many cases, this is due to local pressure not being applied long enough during the blood draw and blood leaking out into the subcutis and tissues, causing local bruising and swelling, and pressure on the tissues, or due to the nerves adjacent to the blood vessels being punctured during the blood draw, or the nerves being directly injured by the puncture needle. In general, there is no need to be overly nervous when such a condition occurs, and close observation is sufficient.