Is there anyways to lock your save file? I just started another playthough and I want to make sure i dont delete my orignal one, anyway to lock it?

If you're playing on PC simply backup your save folder in - Documents\My Games\Skyrim\Saves

You could always locate the file and copy each save that you want to protect somewhere else on your PC, when you want to replay that old character just put a copy of the save you want back.

I got it on xbox . Just another reason why PC is the superior console.

You could probably copy it to a flash drive. Or save your new character to a flash drive.