How to import DB with .sql extension into SQL Server 2012?
From BOL:


  If the database being restored does not exist, the user must have
  CREATE DATABASE permissions to be able to execute RESTORE. If the
  database exists, RESTORE permissions default to members of the
  sysadmin and dbcreator fixed server roles and the owner (dbo) of the
  database (for the FROM DATABASE_SNAPSHOT option, the database always
  exists).


You're creating a database on your server, regardless of the fact that it already existed on another server, therefore you need CREATE DATABASE permissions.