A pus-filled swelling after an insect bite usually suggests that the area has become infected due to scratching, irritation, or bacteria entering the skin. The affected area may become red, warm, painful, swollen, and may release pus over time. To help the swelling heal, keep the area clean by gently washing it with mild soap and water, and avoid scratching or squeezing the swelling because this can spread the infection and worsen the inflammation. Applying a warm compress for 10-15 minutes a few times a day may help reduce pain and encourage drainage naturally. A doctor may prescribe an antibiotic cream or oral antibiotics if the infection is significant, and pain-relieving medicines may help if there is discomfort. If itching is present, antihistamine medicines may also provide relief. Keep the area dry and covered with a clean dressing if pus is draining. If the swelling becomes very large, extremely painful, spreads rapidly, is associated with fever, red streaks, or difficulty moving the nearby body part, you should seek medical attention promptly because it may require drainage or stronger treatment. People with diabetes or weak immunity should be especially careful, as skin infections can worsen more quickly in such cases.