Hi friend, may be your ringtone file is corrupted.so, do one think change your ringtone with so other ringtone. it will help you. go to the profile settings select it.
if it not work again.then, go for pone software updates. one more go for phone reset option. which is available into the phone settings. but, at reset time it ask you for code. that is your security code. Enter it. before it please make backup point to save your data & contacts.

Regards: Rakesh