In expresses more the idea of movement e.g. he threw a book in my face, her hair fell in her face, he looked me in the face.
To these you can ask the question how? because the emphasis is on the action.
On expresses more the idea of position e.g. the light fell on her face, he punched her on the nose, the mud splashed on her face, he put a book on her face. To those you can ask the question where? because the emphasis is on the place .
So to me, you could say both in or on in your examples depending on whether you were emphasising the movement or the position, though as Masood says the more likely is on.