This. I use this trick on many games I want to give a second playthrough without confusing my save files.
If you don't want to use a second account though, copy your current save data to a USB thumbdrive or external HDD for a back up of your current save data, then delete it from your PS3.
Do so from the XMB under Game, it'll say "Saved Data Utility (PS3)" Should be right above PlayStation Store.
If you need help, just ask and I'll help you through the process.