Persistent dull pain, also known as an ACHE, is a type of discomfort that is usually constant and can last for days or weeks. It is often described as a deep, throbbing sensation that can be localized to one area or spread throughout the body. It is usually caused by an underlying medical condition such as arthritis, fibromyalgia, or an injury. Treatment for persistent dull pain typically involves managing the underlying cause, as well as using medications and other therapies to reduce the discomfort.