How do I treat a centipede bite with a lot of swelling and bruising?

Centipede. Wash the wound with water ; soap. You can take tylenol (acetaminophen) or an NSAID for pain. Antihistamines can be used for itching. Pain ; swelling are normal for centipede bites. However, if swelling is excessive or the skin is necrotic then you will need wound care. Check your tetanus status. If you don't know when you last shot was or it has been over 10 years - that should be repeated as soon as possible.
Local care. Wash the area with soap and water. Apply a cold compress for 10-15 minutes. If the area around the bite becomes increasingly red, swollen or tender, then you need to seek medical attention.