To injure is to cause physical harm, and that physical harm is known as an injury.
Ex: When New England Patriots quarterback, Drew Bledsoe, was injured, rookie Tom Brady stepped in to replace him. Brady has never looked back and has become one of the best quarterbacks to ever play football.
Ex: An injury to Rob Gronkowski's arm in the 2012 season forced him to miss the end of the season, but this season with the New England Patriots has been the best of his career.
Injurious is the adjective form of injury and describes action or words that cause injury. Add insult to injury is an idiom that means to make a bad situation worse.
Ex: I found my voice coach's criticism of my version of "Let it Go" injurious to my ego. In fact, I dropped out of my school's production of Frozen.
Ex: When my replacement in Frozen was selected as outstanding actor in the regional competition, it added insult to injury. As a result, I may never sing again.
To afflict is to cause distress or great discomfort. Affliction is the noun form of afflict, and it is great distress or a serious disease. It can also be a cause of mental or physical pain.
Ex: My grandfather lay in bed for several days after his surgery. As a result, he was afflicted with bedsores that were very painful and needed special treatment.
Ex: My mother's cooking is so terrible that it is an affliction we must endure every day. The real problem is that she loves to cook and thinks she's good at it.
The book of Job in the bible details the afflictions he suffered, which included the killing of all of his children and his being covered with terrible sores. Another word for affliction is plague, which is any cause of trouble.
Ex: When someone is described as having the patience of Job, he is likely to have carried on even though he has endured many afflictions.
Ex: In Romeo and Juliet, Romeo's friend, Mercutio cries, "A plague on both of your houses!" He wishes bad things to happen to both the Capulets and the Montagues, the feuding families in the play.