Hello and welcome to Windows Central.
You may try connecting your phone to your PC and then use the Lumia Software Recovery Tool - make sure you select the option that says your phone won't start up. This should be an attempt to reinstall the OS of your phone.
If that doesn't solve the problem, you may want to consider taking your phone to a service center. Make sure to bring your official receipt with you, since service centers honor warranties if your device is indeed still under warranty (usually 12 months after purchase, but can go up to 48 months depending on the package and store).
Should you wish to ask further questions, please don't hesitate to create a Windows Central account and respond in this thread.
08-14-2015 08:24 PM