Terrible rattle coming from front passenger seat

Hello!

I own a 2011 Sienna LE (our third Toyota Sienna). Last week my 10 year old got ticked off about something and kicked the back of the front passenger seat out of frustration (about 2 kicks). He sits directly behind it. Yesterday an extremely loud rattle started in the seat. When someone is sitting in it, it's fine. But when no one is sitting there, it rattles and rattles LOUD. From the time the car starts until the car is turned off. It's even worse over any bumps in the road. The problem is, the part that is broken is inside the seat. Will Toyota be able to fix this? Will it be covered under warranty?

Thanks!