Do not be Nervous.  Keep Calm. Pick up the tooth by the crown or top par

t and you may rinse it with water to get rid of any debris without rubbing the root part.  Try to reinsert in the socket.  If you are unable to do this, place the knocked out tooth inside a small container with milk.  The container should be covered to avoid contamination. Time is gold, call your Dentist right away. 

Also check  KNOCKED-OUT TOOTH