How long have you owned the phone for may I ask as their maybe a cooling off period ?
If this was my situation I would contact the seller and ask what options you have to choose from.
Other avenues could be to fit a glass screen protector onto the screen that would possibly hide the scratch.
My recommendation is the Whitestone Dome Glass Screen Protector.
The Manufacturing Warranty wouldn't cover a scratch as this could be seen as accidental damage unless it can be proved the scratch was already on the phone out of the box which is something you may find hard to do.
This is why I personally purchase my Samsung Phones from my local bricks and mortar Samsung Experience Store and open the phone in the store.
On a side note sometimes a phone that's been purchased elsewhere may not be covered in regards to the 24 month manufacturing warranty. Please do check.