A bulge in the needle is caused by the needle puncturing a blood vessel or the needle slipping outside the blood vessel, resulting in extravasation of the drug into the subcutaneous and tissue spaces. The needle should be pulled out immediately, and the injection should be re-injected in a new place, while the bulging area should be pressed by hand to prevent further bleeding. A cold towel can be applied externally within 24 hours to effectively reduce the exudation of tissue fluid; a hot towel can be applied externally after 24 hours to promote blood circulation and the dissipation of local bruising. Patients can also apply ginger or potato slices on the surface of the bulge, and replace them when they are dry. Alternatively, magnesium sulfate can be applied externally, and if necessary, hydrocolloid dressing can be applied externally. If it contains irritating fluids, such as chemotherapy drugs, should be played locally closed for treatment.