I just went through the same situation last week. Had a flat in my rear driver side tire (tiny puncture/hole in the inside corner). Put the vehicle on my lift and also discovered the rear passenger side tire had both a screw and a nail in it (but was not leaking). So, I decided to replace both rear tires. I’m at 24K miles on the current tires with about 60% tread life remaining.
The general rule of thumb is, if all your tires are relatively new (still have a lot of tread life left), then you can just replace the one tire that is punctured. If you have around half the tread life left, then it’s a good idea to replace two tires on the same axle/motor, to provide better overall balance. If all your tires have only around 25% tread life left, then you should probably replace all four tires. No hard, fast rule about when to replace one vs two vs all four tires. However, I spoke to my Tesla SC, as well as a few other tire shops, and they all share a similar view to what I described above.
Good luck!!