You've probably damaged the driver diaphragm. Not sure if they'd cover that because technically it's not their fault and is mishandling on your part.
Why not just send it in, without mentioning how that happened? It's not like you can still enjoy it as it is. Best case scenario you get a new pair; worst case, you have to buy a new one, but you spent about $10-$15 sending it back.
Is it just the cable, or is that shadow inside the driver some kind of residue?
In any case if it's just the cable it's easy enough to damage cables even on daily use; if there's residue inside the driver housing and they won't even need to take it apart to see it (I would have otherwise gambled the shipping cost on the chance that they also would just try to hasten the replacement processes and not look too closely) then there's really no point in posting here, you'll just have to buy a new one.