What are some things i can do to care for a tooth cavity before i see a dentist?

Limit candies: And sugar rich foods and liquids. Brush and floss properly. Make sure to see your dentist asap to have the cavity treated prior to it becoming a root canal.

Keep it clean: You should see a dentist as soon as possible, as cavities can get worse. If you wait too long, a simple filling many turn into a root canal, or worse - an extraction. I hope you don't delay seeing a dentist too long. In the mean time, keep it as clean as possible (brush/floss), and stay away from very sugary and acidic, as well as hard foods.

Brush and floss: If your cavity is past the enamel layer there is nothing you can do. It will progress, get bigger and eventually lead to more expensive treatment and more tooth destruction. Root canal. And tooth loss.