You'll need to go to an authorized service center. I doubt scratches are covered under warranty though

Hi guys just wanna share an issue i highlighted previous regarding iPhone warranty. I have checked with QCD service centre in Berjaya Times Square and Mac City service centre in 1 Utama. Both have confirmed that iPhone warranty is not limited to the country you bought the phone but rather to the part number of the phone itself. In other words, u can provide them ur iPhone serial number for them to check in their system (not the warranty check from apple website). If the part number is available in Malaysia, means the warranty is covered here. To prove this point, I have successfully claimed warranty and was given a replacement phone for an iPhone 6s Plus that was bought from Apple Store in US. I hope TS can update regarding this warranty. To be safe, of course it's better to buy from Malaysia. but we should debunk the myth that iPhone warranty is limited to the country it's bought. Not anywhere was it written in their T&C. Those early adopters can quite safely be assured buying from SG or US Apple Store sets.

AND i have checked with Apple themselves through their recent twitter support team. Their iPhone warranty are global.