As someone from the other side - let them know about the issue ASAP. Telling them several days/weeks later will make them (reasonably) suspicious that it was not a pre-existing issue.

Then work out a plan to handle it (possibly including a screen protector and deferred replacement). Small ops have real people doing customer service. They won't want to *have* to send you a new phone right away and are very aware of costs; being reasonable and flexible is appreciated in my experience.