iPhone 13 ear speaker not working after update

To rule out, that the iOS software caused the issue, reset the iPhone to factory settings, and in case the backup data is corrupt, set it up as a new device and test the ear speaker again.

Restore your iPhone, iPad, or iPod to factory settings using a computer - Apple Support

If the speaker works after that, restore from the latest backup and test again.

In case the speaker does not work after setting it up as a new device, this is a hardware issue and the iPhone has to be serviced:

Apple - Support - iPhone Repair and Service

You can also get the iPhone inspected by an Authorised Apple Service Provider next to your place.

Apple - Find Locations

Did you already have a look at the general troubleshooting?

If you hear no sound or distorted sound from your iPhone, iPad, or iPod touch speaker - Apple Support