Towards the end of the movie, when Frodo and Sam are walking towards the volcano, Frodo has a gash on the right side of his face, but nothing on his left. Then, when Sam is holding him, asking if he remembers the taste of strawberries, Frodo's gash is on his left side, and he turns just enough you can see there isn't one on his right. Then, when they are up again, and through the next few scenes, the gash is back on his right side.