You probably tried to upload too large file. Please refer to documentation for ways to workaround this limit. Error when trying to import a file in MySQL.
A workaround for this is.
Get the MySQL backup and if zipped e.g. database.sql.gz, then unzip it.
Now go to your sql.exe in a windows command prompt.
$ cd xampp\mysql\bin
$ C:\xampp\mysql\bin>mysql.exe -h localhost -u root -p
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 826
Server version: 5.5.15 MySQL Community Server (GPL)
Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> use [database name]
# Enter here the backup SQL file location
mysql>source C:\Users\[Your Name]\Desktop\[Database Name].sql