Actually he is allowed to use the title of President Elect per the Presidential Transition Act of 1963:
The terms “President-elect” and “Vice-President-elect” as used in this Act shall mean such persons as are the apparent successful candidates for the office of the President and Vice President, respectively, as ascertained by the Administrator following the general elections held to determine the electors of the President and Vice-President in accordance with title 3, United States code, sections 1 and 2.