In Australia, no form of physical damage is covered by warranty.
Warranty only covers things where the manufacturer is at fault, and clearly you are at fault not Sony.
Also, that scratch is ... not really noticeable haha, i had a million of those on my (now dead) Z1.
Sony Xperia Z1
[Partially inactive on xda due to studies]
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Nokia 3110 > Nokia 6100 > Sony Ericsson K750i > Nokia 5310 Xpress Music > Nokia N97 Mini > Sony Ericsson Xperia X10i > iPhone4s > Sony Xperia Z1