Quoted from P2K:It looks like the cabinet corner itself has come apart and the split is a symptom. What does the outside look like?
I think you need to use Gorilla Glue and large clamps (or a band clamp) to close up that split.
Alan
Agree, but wonder about Gorilla glue over Titebond wood glue. Gorilla for me has not been a good wood glue.