Oil canning in flight is common, especially on the top surface of a wing. Sometimes you won't see it because of the ambient lighting such as flying under an overcast. However, sunlight from certain angles can really accentuate the visual effect with shadowing and make it appear startling, or one wing worse than the other when in fact, they aren't.
Oil canning on the ground, especially if you can flex or "pop" it by hand can be an indication that a surface or structure has been under stress or improperly constructed.
Flying Boeings, I had a few pax over the years express concern about seeing it on airliner wing panels, and a couple of those were GA pilots.