If i have a light tooth cavity, what should i do?

Light tooth cavity?: Never heard that term if your talking any type of cavity small or whatever get fix any cavity will get larger. Incipinent is just a slight penetration of the enamel it still needs to be fixed.

Get a filling: A cavity only gets deeper and larger unless fixed. Thus you need to get it fixed by getting a filling a the dentist, otherwise the larger it is the more expensive it gets.

See a dentist: The longer you delay tenant the worse it will be for your tooth, your health and your wallet.