Get a class II restoration done by a dentist as early as possible. If there is sensitivity in that area, caries may have slightly reached the pulp. Go for pulp capping also along with restoration.

Hel we can see in the image there is a cavity which require filling. The  dentist will take a X-ray if needed and than do a filling. Right now it is open and whatever you eat or drink cause that sensitivity and gets filled in that area. More delay can lead to root canal treatment in that tooth so better get it treated as soon as possible.

Get a filling done quickly. It hardly takes an hour Health comes first before any exam. If you leave it like this any longer you might need a root canal treatment...which will be more time taking and expensive

Get it filled asap

Please get your cavity filled

Prevention is better than cure. Since now u have only sensitivity better prevent pain by filling the cavity. That will reduce your sensitivity too. Keep good oral hygiene to prevent it from deepening by brushing atleast twice daily if u don't have time to visit a dentist.