Now don't worry yourself.....
Next time you fly you will see the same patches on A320's and similar on other aircraft.
Theses patches are rub or wear strips placed on the flaps upper surface.
Chafing of the flaps by the spoilers or trailing edge wing extensions is permitted while using sacrificial paint or thin stainless steel plates bonded to the wing.
Looking across from the inner flap to outer you can clearly see were the chafing has polished the wear plates.
The 'crack' on the inner flap appears to be a collection of grease, oil and atmospheric dirt at the point of flap to wing contact.
Hope that is what you are looking for??
