Yazid was asked about the wounds the Prophet ﷺ suffered on the day of Uhud. He said, "The Prophet's ﷺ face was wounded, his front tooth was broken, and the helmet was shattered upon his head. Fatimah was washing the blood while Ali held the water. When she saw that the bleeding only increased, she took a mat and burned it until it turned to ash, then pressed it against the wound, and the bleeding stopped."
أنه سئل عن جرح النبي ﷺ يوم أحد، فقال: جرح وجه النبي ﷺ، وكسرت رباعيته، وهشمت البيضة على رأسه، فكانت فاطمة تغسل الدم، وعلي يمسك، فلما رأت أن الدم لا يزيد إلا كثرة، أخذت حصيرا فأحرقته، حتى صار رمادا، ثم ألزقته فاستمسك الدم.
Bukhari narrated it in Jihad (2911) and Muslim in Jihad (1790:101), both through Abdul-Aziz bin Abu Hazim, from his father, who heard Sahl bin Saad, and he related it.His saying "the helmet" refers to the headgear worn on the head. His saying "was smashed" means it was broken, and hashm means breaking something dry and brittle.