Pain in the arm after a blood draw may be related to the following reasons: 1. Pain at the puncture point. Because of the thickness of the needle used to collect blood from a vein, there will be significant pain when it pierces the skin and subcutaneous tissue. Generally, this condition will gradually improve in a day or so. 2. Blood leakage around the puncture point. After the venous blood collection, the local pressure is not exact, and the blood leaks out to the subcutaneous along with the puncture point, forming a bruised hematoma locally. In this case, the absorption of the hematoma can be promoted by applying cold compresses with local ice packs, which will generally be completely absorbed in about three days.