Just a few questions to maybe provide a better answer.
Where did you buy it and how did the screen crack? If it was dropped then it's not covered under warranty. There are very specific looking cracks that can result from a manufacturing defect that can be covered under warranty, but those are rare and easy to spot.
And if it was a gray market phone (purchased retail in one country for resale/use in another) the only way to receive warranty service (or possibly even out of warranty service from Apple or an AASP) is by getting service in the country where the original retail sale was recorded. They likely won't even perform a factory authorized glass replacement service in that case.