What could be causing white spots on my MacBook Pro screen?

Moisture or liquid damage is one possibility, though white spots alone aren't enough to confirm it. If liquid may have reached the screen, have it checked before assuming the display needs replacing.

If the marks don't go away, you may be able to keep using it if the rest of the laptop works normally, or get a repair quote for the display.

Don't put the laptop in rice. It can leave debris behind and isn't a reliable way to dry it. Silica gel packets have been suggested for moisture, but they aren't a guaranteed screen fix.