Hot compresses. Some acne lesions are large, ugly, and may be painful. You can try to treat it at home by yourself, with hot towel compresses and by rubbing a Benzoyl Peroxide Gel into the spot several times a day. You can buy this without a prescription. If it is not better, and you have a special event to go to, you must visit a dermatologist who can give you an injection of kenalog (triamcinolone) right into the bump.
Good question. A pustule from an acne lesion is unsightly and at times painful and one has the urge to do something, especially if a social event looms. Scrubbing with soap and water and cleaning with alcohol with good clean hands and a sterile needle, one can often gently pierce the head of the pimple and using a gauze or cloth, gently express it. Then apply alcohol, witch hazel or astringent and use ice pack.