7 Make a new layer and name it "stitches", and start to draw lines across lips using brush tool. Try to make it so it looks like stitches

Now add some add some lights (white color) on the stitches.

8 Now blend it with "Smudge Tool (Shortcut: R)".

9 Make another layer and name it "some adds". Start to draw a crack look a like on the stitches holes.

Now change this layers blending mode to "Color Burn"

10 Make another layer and name it "stitches shads". Start to draw shadows on the bottom of every stitches with dark color but not black just try to use "Eyedroper Tool (Shortcut: i)" and click on the darkest area around the lips.

11 Make another layer and name it "Tears", I already warned you that there's gonna be loads of layers.

Now start to draw some blood tears on the bottom of the eye. Again make it a little but smooth with "Smudge Tool (Shortcut: R)" and then change the layer mode into "Overlay" mode.

12 And you're done, you have successfully converted a good pretty girl into very horrifying character. You can try other images with different blending options.