Four centimeters, I suggest you sew a needle! The wound is so big that it will take a long time to heal without sewing. Besides, it's the head, not anywhere else, 4 cm, which is a bit serious. Four hours later, there was still blood oozing out. I suggest you go to the hospital to have a look to prevent intracranial hemorrhage and arachnoid hemorrhage.

Even if it's no problem, go to the hospital.

I disagree with any of the above comrades. Anti-infection is not necessary in places with rich blood flow, and sometimes anti-infection is more important. For example, triangular areas of the face are particularly susceptible to infection. There have been cases where someone died of a small boil infection on his face. Head blood infection is easy to cause brain infection.