To determine the polarity of the molecule, there are two requirements. The first one has a variety of terminal atoms, whereas the second has a lone pair on the center atoms. The molecule is polar if one of the requirements is met; else, it is nonpolar. The oxygen atom is a terminal atom because it surrounds the sulfur atom, which is the center element in the SO2 molecule's Lewis structure. In this molecule, there are two terminal oxygen atoms. If we look at the first criterion, we can see that it is not met because it calls for the presence of two separate terminal atoms.
