Pain is a feeling triggered in the nervous system. Pain may be sharp or dull. It may come and go, or it may be constant. You may feel pain in one area of your body, such as your back, abdomen, chest, or pelvis. Or you may feel pain all over, such as when your muscles ache from the flu. Pain can be helpful in diagnosing a problem. (Effective Healthcare) AHRQ has research, tools and resources on pain management and how clinicians can help their patients with pain issues.