Mods are aftermarket modifications to the game. It will depend greatly on how you installed it, what the mod does, and how the mod works. The best starting place is to go back to where you got the mod and see if there are any directions to how to uninstall it. If it is an add on, then you may can simply find where it placed itself and delete it. If it modded files then you may can verify game install through origin and it may correct the game, getting rid of the mod. If it used a mod install program, you may can simply run the program and ask it to uninstall it. But honestly, this forum is about help of vanilla(unmodded game) and we may can offer some advice, changing the game is on you and is up to you to fix when it breaks.