Weird marks on the face.

@NikkiAndTeo , like @Psychotps stated this is an effect that is under Face and then  Skin Details in CAS. However,  in order to change a Sim that is already made, you will need to use some cheats.😉
First bring up the cheat box and in it type testingcheats on and press Enter
Next type in the cheat box cas.fulleditmode and press Enter
Then Shift-click your Sim and choose the Edit in CAS option.  
From there go to Face, then Skin Details, and you will see at the right a picture of a full Sim with the Realm of Magic icon in the corner. 
To disable testingcheats, bring up the cheat box again and type testingcheats off and press Enter. 🙂

(Also, if your Sim was also green , then this would be the Curse of Repulsiveness , which usually happens when making a potion and your Sim fails at that potion. But this curse will also make it hard for your Sim to socialize because everybody around your Sim will become disgusted with their appearance.  However, there is a Curse Removal potion that can cure it as well as a cheat,  Traits.Remove_Trait Trait_Curses_Repulsiveness . )  But since your Sim isn't green then you shouldn't have to worry about that unless they fail at making a potion. 😉