If the photo(s) the OP took are dated/timed shortly after the flight arrived, I would just go back to the airport with the damaged bag -- do not remove the claim check -- and make a claim.

A few months ago, after I arrived home from an AA flight, I noticed (repairable) damage on a valet-checked bag. I took the bag (empty of contents) back to the airport the next day, and AA cheerfully processed the claim. I received my repaired back about two weeks late.

For a bag that is not repairable, the problem, of course, is how much WN will pay for the loss.