I was changing my cam sensirs on my 2008 f150 5.4l triton. When doing this the back piece of the sensor broke off and fell into the engine. What do i do?

Where in the engine? You can't leave it. You'll have to figure out a way to retrieve it. This is also a great example as to why having work done at a repair shop by certified technicians is the best choice. They have the tools and resources needed and don't have this kind of thing happen generally. Now, the other thing -- why were you replacing these sensors? They were almost for sure just fine. www.repairpal.com/repair-shops