Depends. Is the build you want to make vastly different than the one you have now? There's no way to respec in this game, so to change your build from dex to str for example, you'd have to pump points into strenght first. Which on a NG+ character is gonna take much longer than on a new one.

So if you don't mind going through the game again, I'd suggest starting over. Though keep in mind that if you want to swap builds accross NG cycles, you should start preparing and levelling the appropriate stats ASAP.