White smudge on camera lens

Generally, the optics cannot be disabled to be cleaned. Please take your iPhone to an Apple Retail Store or Apple Authorized Service Provider. They’ll need to inspect the device and determine if a repair or replacement is required.

If you’re in the US, please call  1-800-MY-APPLE, or outside the US, consult the support articles below. In Canada, call 1-800-263-3394.

Contact Apple for support and service - Apple Support

Genius Bar Reservation and Apple Support Options - Apple

Explore Service Locations

Do you have some kind of external lens protectors on? If so, please remove them. They are easily damaged and severely reduce image quality.

What model iPhone is that?

The only thing I can suggest in addition to what Jeff Donald posted is wait a while (a few hours) and see if it disappears. I think iPhones are pretty airtight but yours could be aging and losing some of that. If that's the case, if you brought in the device from a cold location into a humid environment it could be condensation.

What color iPhone 17 is it?