problem description

git, hosting platform under

uses the code cloud;
has only one main branch of master;
colleague"s code pull has gone wrong. I ignored the mandatory error for him, pull down, and then put the local push on;
results that his code is not up-to-date but replaces the latest one; after
, his version has lost a lot of files.
my code has a local backup before pull. What should I do if I force my code to be the master version on the server?