This is a good question. Since the cause of Jimmy's problems, i.e., his anger, has a specific beginning in time and involves specific incidents to which Jimmy was only a witness, his problems cannot in any way be said to be self-inflicted. Jimmy explains that his anger is caused because he sat by his father giving comfort while his fther slowly died over the course of many months from wounds inflicted in the Spanish Civil War. While he was dying, Jimmy's father never stopped talking while trying to reconciled the parts of his life before it all slipped from him. This constitutes a large personal psychological cause to Jimmy's anger.
There is also a large social cause to Jimmy's anger, which again can't be called sefl-inflicted in nature. John Osborne is very particular in saying that Jimmy's father died of wounds from the Spanish Civil War. That was a war that England took no part in. Egnlish citizens who disagreed with England's non-intervention policy volunteered as mercenaries to fight in Spain against the Fascist Franco. Such persons were idealists who were fighting for a belief in democracy. Jimmy's idealist father only received a death knell for himself and tragedy for his family as a result of his idealism. It must have been difficult for Jimmy's father to sort out his idealism and social beliefs while he laying dying in front of his son.
So while Jimmy's problems can be identified as personally psychological and social, they cann not be said to be self-inflicted. It may be said, however, that he may have made poor choices as an adult about how to live with his experiences and trauma, but that is still a long way from self-inflicted problems with anger. this is why the title is Look Bsck.... The causes are from his past experience, thus are not self-inflicted.