Cracks and other damage to an iPhone's screen is considered cosmetic in nature and isn't covered under Apple's limited warranty for the iPhone. By assessing the extent to which any screen crack that occurs limits the functionality of the iPhone, you determine whether or not the out-of-pocket repair cost is worth incurring. Alternatively, your cellphone company's insurance policy may cover screen damage.
Severity and Cause
After you first notice a crack in the iPhone screen, assess the severity of the crack and attempt to determine the cause of the crack, if it hasn't occurred in the wake of accidental trauma. If you carry the iPhone at the bottom of a purse or bag, for example, a small crack may have developed and grown gradually due to the constant weight and impact of other items in the bag.
If you determine that the crack doesn't impede use of the iPhone and find a way to prevent it from growing, continuing to use the iPhone as normal may be a good option for you. Note that the bigger the crack becomes, the more chance there is that an eventual repair will include a full screen replacement, so only hold off on repair as long as the severity of the crack remains minor.
Once you determine that you need to repair the crack, get an estimate to determine how much the repair will set you back. Visit an Apple retail store or an authorized Apple repair representative to determine firstly whether a replacement is necessary and secondly how much the repair will cost you, regardless of the nature of parts and services required.
Although Apple's warranty doesn't cover accidental damage such as screen cracking, your carrier's insurance policy may include a provision on such damage. To determine specific coverage for your plan, which may vary by geographical location, peruse your contract materials, or if you don't have them on hand, contact a customer service representative from your cellular carrier to find out if the phone is covered.