Hi Natoma,
The Sun isn't really changing in size, but it is not solid so the surface might slightly vary in size in localized regions, esecially when there is a solar storm event. However, the Earth's distance to the Sun isn't exactly the same all year round since the Earth orbits in a slightly elliptical orbit (as opposed to an exact circle), so the Sun's size (as viewed from observatories here at Earth) appears to slightly change. When the Earth is slightly closer to the Sun, it appears a little bit larger, and when the Earth is slightly farther away, the Sun appears slightly smaller. This is a result of how close the Earth is at different times of the year instead of a real change in size at the Sun.
A large object headed toward the Sun would experience a tremendous amount of heat and energy and would burn up before making it to the surface.
Hope this helps!
Holly