Feeling pain in the arm after a blood draw should be caused by local irritation of the arm. It is a normal phenomenon, but it is not obvious in some people. If a sore feeling in the arm occurs, you can massage or apply hot compresses, while taking proper rest and paying attention to maintenance can be done. If only pressure is applied after the blood is drawn, when the needle holes on the skin are not pressed to the needle holes of the blood vessels, the blood will flow out from the needle holes of the blood vessels and pool in the subcutaneous tissue, which happens to be rich in subcutaneous nerve endings and will produce pain if it is stimulated. So to handle it correctly, press the cotton swab straight at the pinhole, so that the pinhole of the skin vessel can be blocked at the same time, and the bruised blood will be absorbed by the tissue naturally after some time.