Abu al-Zinad (may Allah have mercy on him) said: I heard the senior jurists of my time say: Every bone that is broken by mistake is to be set; if it becomes straight and there is no defect, then the offender owes only the cost of treatment. If, after being set, some defect or deficiency remains in it, then there is a diyah (blood money) upon him according to that defect, which people of understanding and insight will determine. Likewise is their view about a deep wound and all the wounds of the body: if they heal and no defect remains, only the costs of treatment are due from him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الديات / 16337