You can treat both your internal and external wounds by consuming a treatment, such as a medicinal herb, or by visiting a doctor in a local town and paying him to Heal you.

To consume a treatment, right click on it or put it in your quickslot bar and press the correspoding key. Treatments will be destroyed when used. It may take time for your wounds to heal, and you may not be capable of consuming other treatments during that time.

You can buy treatments from any doctor.