Bruising in the nail is mostly caused by external damage to the nail area. Most commonly, the nail at the bleeding site may have been hit by some external force or squeezed by an external force, resulting in the formation of bruising under the nail. Of course, in addition to these external factors causing nail bruising, it is also possible that the patient may have some impairment of peripheral circulation, which may result in the formation of subluxation of the nail. This bruising can be in the form of pitting or flakes, or even extending to the nail root and the surrounding area of the nail. Therefore, if a reaction of bruising under the nail occurs, it needs to be actively examined to prevent a secondary bleeding reaction.