May be nice to run sudo su beforehand so you have enough permission.

Run groups to check if you have a group with your name:

sudo usermod --move-home --login new_username --home /home/new_username old_username

If you did have a group:

sudo groupmod --new-name new_username old_username

To make sure old references work temporarily, you may want to add a link:

ln -s /home/new_username /home/old_username