How to get ink from my iphone camera?

So I left my phone in my pocket and my pen was in it but the pen exploded:/ I've tried nail polish remover but it didn't do anything:/ its only on the back camera… Also how much would it be to get a new screen and also can you get a new back? Cause it all Stained ;-; iphone 5 back btw.

Moisten a cotton ball or soft cloth with the rubbing alcohol. Rub it over the surface of the stain until the ink is removed. There's no need to apply excessive pressure, just continual rubbing will remove the ink.
Once removed, dry with a soft cloth.