Hi , I understand your concern. From what you are describing, it seems like your child has a hematoma, which is a collection of blood that occurs after mild injury or fall, or a dermoid cyst which occurs in some children. You can consult a pediatric surgeon if the swelling does not come down in a week. Meanwhile, if the swelling is rapidly increasing in size, or your child has pain/increased crying or pus discharge from the swelling, take her to the hospital to see a pediatric surgeon. Hope this helped you..!