If you drop an iPhone in an apple leather case and there's no external damage, and the first time you unlocked it after the drop, there was a slight delay for the home screen to show, could this be a sign of internal damage?
It works. I just tried it with 3D Touch. On older iPhones, dropping it sometimes caused buttons such as lock switch to break or dust to get into the camera lens.
No need to worry. If there is no exterior physical damage and you phone is working perfectly, you are good. The delay you experienced just happens sometimes.