How do I clean stain off of iPhone Leather case

Looks like a water stain. You might have some luck with mink oil but, it will darken the leather quite a bit and it may not hide the stain completely..

 

Unfortunately at this point, hiding the stain is the only way of making it less or completely unnoticeable. This can only be done with an oil or conditioner which would make it darker. Any cleaning products would just ruin the case. I guess you could try getting the leather wet with enough water to try and blend the stain to the surrounding area..

 

If you had it for less then a year, just do a warranty exchange.

 

Let it ride, it adds character!