A trip, a fall or blow can cause bodily movement of the tooth. This is normally backwards, such that you have difficulty closing your mouth, but sometimes it can be knocked forwards such that you look buck toothed.
Firstly don’t panic. You need to get to an emergency dentist as soon as possible to try and move the tooth back into its correct position. Delaying this can lead to permanent damage to the blood supply of the tooth and increase the risk of complications at a later stage.
The dentist will thoroughly examine your injury, and take x-rays to assess the extent of damage and to ensure no other damage to adjacent teeth or complications are present. Normally the tooth is manipulated into position, and splinted with a “brace” to help hold the injured tooth in position. The brace may need to be left from between 2 to 4 weeks, depending upon the type of injury sustained.