From OCP 8 exam topics
Create inner classes including static inner class, local class, nested class, and anonymous inner class
For me, nothing about an inner interface.
But there can be an inner abstract class (as a member inner class, a static inner class or a local inner class).
I think, the main difference between an inner abstract class and an inner interface is that the inner interface can not be declared as a local inner class. This ist the only information I would remember in this topic.