Most likely, you damaged the hardware of your iPhone X while dropping it. The best solution is to bring the device for a check to an Apple Store.
Tip: Before you get to the service, make sure to:
- Have your Apple ID password ready
- Bring your sales receipt (if possible)
- Bring a form of personal identification
You can also call to check whether you need an appointment before you go to a service location. For example, schedule a Genius Bar reservation before you go to an Apple Store.