What caused a toe to turn black? Shoes too tight?

A Hematoma. A hematoma is a blood blister and if found under the nail, is called a subungual hematoma. It can cause the toe to turn black and is typically the result of pressure on that site - can be from a shoe and/or something dropped. However, it can be from a shoe that is either too tight or too loose. In loose shoes, the foot shifts in the shoe and can hit the end. Have it checked by the podiatrist.
Black Toes... When a toe turns black, it has usually died from lack of blood supply. When a part of it turns black, like under the nail, it is usually the result of a bruise and will eventually grow out. Melanoma can involve an entire toe if left for too long. It's best to have it checked out professionally.
Possibly. Tight shoes could cause the toe to turn black. It could be a hematoma from some type of injury. However, a toe turning black is typically not normal and could be problematic. You should see your podiatrist.