As @TheShokBlok said, changing account names is one of the supporter features: You can even change your name every 30 days if you like, so you don't have to live with eternal regrets if you don't like the next name you come up with anymore later along the line... ;)
Details here:
https://www.newgrounds.com/wiki/help-information/supporter-upgrade
TheShokBlok
luckily for you, there are plenty of options to choose from!
1- get supporter.
2- pray that someone else gets you supporter.
3- start another account from scratch.
4- live with the consequences of your actions.
darkdude1234
fourth one is the most accurate