So proximity sensor now detects object getting close, but don't recover when object is moved away. The sensor reads 100 when it should be less than 10.

I have read this is a very common problem, and is due to the dirty sensor, problem is how to fix it.

Now, I tried compressed air from audio jack, didn't work. I also do not want to root the phone and cause problem with upgrading down the road.

Any possible fix, calibration? Or I just have to live with it?

@T-Mobile GN3