It sounds like you just need to update the name of the remote branch that your local "master" branch is tracking. You can do this with the following command:
git branch -u origin/main master
This will set your local "master" branch to track the "main" branch on the "origin" remote. You should then be able to pull changes from the central repo with:
git pull
If you still encounter issues, you may need to reset your local "master" branch to match the remote "main" branch. You can do this with:
git fetch origin
git reset --hard origin/main
This will overwrite any local changes you have made to the "master" branch, so be sure to commit any changes you want to keep before running this command.