What is the ruling on praying with a small amount of blood from a wound in the private area, without performing istinja (washing after using the toilet) or changing clothes, and sufficing with wudu (ablution), believing that the blood from wounds is pure on the body and clothes?

Blood from wounds is impure, similar to menstrual and postpartum blood. Praying with it, if one is aware of its presence, invalidates the prayer unless it is a small amount. The small amount of blood is estimated by the area of a Baghdad dirham, which is the view of verified scholars, or by what is not excessive, or what is conventionally considered a small amount. However, if one prays while unaware of an amount that is not excused, some scholars hold that repeating the prayer is obligatory, while others do not.