Finishing touches! At some point it's a good idea to add a drop shadow to the zipper and you can also change the effects on it to bevel it so it looks more real.
I took a soft brush with a very low opacity and 0 level of hardness, then sampled the color of the cheek where I wanted to highlight, then changed that color to make it slightly brighter - then used the brush to make some highlights on parts of the cheek. I did this to make it look more real and a little shinier in spots.
I used a "scar" brush to make the skin near the top of the zipper look a little indented. The brush was downloaded online - then I made the color of it the skin color and messed around with the effects - adding a little bevel to make it look like it does.
The scab on the cheek was also created with a brush!
If you have any questions please let me know. I tried to make a video tutorial but my software wasn't working so I tried to make these graphics as detailed as possible! Good luck!!!