O- boy I do not want to get a cavity!
You can prevent cavities by brushing your teeth, I recommend 3 times a day. Use chewing gum containing xylitol.
Cavities can be reversed if you start soon enough. I use fluoride and MI paste, believe it or not if you are fast enough you can reverse a cavity.
If your too late then you better see your dentist for a filling and or crown. I prefer gold myself!