Did you recently perform an update. I see you are using iOS 26 that was just released today and you should expect your phone to be hot for several days, and not unusual for it to take a week for the indexing to complete. If you were previously using the beta version of iOS 26, that is expected as well through the entire beta process.
Your phone does have temperature sensors in it and will show a thermometer on the screen and shut down when it gets too hot. I assume you are not seeing that.
Stay tuned there will be many users saying the same thing for the next week after the update, then those posts will gradually go away. The same thing was seen on iOS 18, 17 and previous iOS updates. It was predicted here as well to get ready for the battery heat and battery draining posts after the update.