If the inner door glass just cracked but still in place you probably can use the oven for cooking but not for the self cleaning.
Due to safety issue it's better to replace it.
This part is not too difficult to replace yourself.
Remove the door from the range and place it on a flat surface with the front of the door facing down.
Remove the screws holding the inner door panel and remove the panel.
The inner door glass comes as a kit and it is much easier to understand the replacement process when you will see the kit.
- The part number for the inner glass kit is
AP3124577
Here are the break down diagrams for the Kitchen Aid range
Model KGST307FWH0
Gene.