A surface bruise will usually result in concentric rings (Herzian ring cracks - as mentioned to us by Alan T. some while ago) around the main impact area. These can penetrate a fair distance below the surface and would appear as rings (but looking quite "silvery") rather than as "flakes".
From the look of the damage in the photo, it seems to me that there are no clear rings, but two "flakes" of somewhat irregular shape. That is why I thought it would have been an internal stress fracture.
But then I guess that "flaky" internal fractures could result from an external impact stress without leaving the usual concentric rings of a bruise.
Whatever the "damage" really is, I don't think it's just air bubbles.
Edited to add photo of what I call a "fairly typical bruise" (in an Antique Clichy weight).