Seek professional help. An exam will be necessary with radiographs (X-Rays) to assess the damage. The fix can be just bond the other half back on or build the tooth back with bonded composite (tooth colored material used in filings), a porcelain veneer or even a crown. Most importantly is to test the tooth vitality to verify you won't need a root canal. Know that whenever a tooth receive trauma there is an increase chance of the tooth become darker. In this case a porcelain veneer or crown should mask the tooth color. There is also the possibility of tooth whitening. All these options to be determined by a Dentist. Hope this helps!
Hope this helps!