iPhone 6 rebooting itself after I dropped it.

Hi! My first time asking a question here. So I accidentally dropped my iPhone 6 and it shut itself, I rebooted it just to see the battery percentage is way lower than it was prior to the drop. I then notice that my iPhone fails to make a reading of the battery and everytime it does: it shuts itself. My hunch is that maybe something in the inside like the motherboard got damaged or the battery is about to get bloated (i had a battery replacement on this iPhone) but I’m a no-brainer when it comes to this.

EDIT: Apparently, the chances of having the iPhone to reboot itself become very low everytime the percentage is around 80 and above when charging . And I didn’t mention this before but I checked the “Battery Health” in the Settings and it said it needed service, but then it changed to the status being 100% when the percentage is above 80