The first thing to do is to calm down your child so that you can take a look and see what has happened. Teeth that get hurt badly can be sensitive to touch or be broken, and the gums can bleed a little. If the tooth is broken, try to find the broken piece as it can possibly be reattached. Also, the lips and inside of the cheeks can be cut by the sharp edges of the teeth. To try to "self-diagnose" the problem, a good reference that Dr. Schafer uses is The Dental Trauma Guide. This website is extremely detailed, and although it's mainly meant for dentists, most lay people can understand it as it is well laid out and has well-labeled pictures.
Make an Emergency Dental Appointment
If your dentist is open, you should call to make an appointment as soon as possible. If you believe that your child needs immediate attention and it is after hours, you should take your child to New Orleans Children's Hospital as generally, a pediatric dentist is on call or another local children's hospital that has a dental clinic associated with it. Thankfully, as kids generally heal well and the mouth probably heals faster than any other area in the body, most trauma can be handled with little long-term consequences.