It suddenly popped out, is it fixable or needs to be replaced?

 

Check your owners manual, It has the procedure to reset it.

 

i checked and tried to reset it, but apparently, some part was actually broken from with in.. need to replace it

anyone know where i can order it from

 

 

That's a safety feature for whiplash protection when struck from the rear. Several weeks ago my '12 was rear ended and both front seat headrests popped open like yours did. The repair shop put it right but didn't explain how. I'm sure your dealer could remedy the situation.