I have an exterior door which is wood (with a glass window in the
middle). It was unstained wood when it was installed so I stained it
with a stain/waterproofing product. I think, unfortunately, I forgot
to stain the bottom of the door.

Over the last couple weeks it has gotten harder and harder to open.
Now it won't close. I checked the hinges and they're all still tight.
I can see the marks from the door jam on the door where its rubbing.
Should I use my electric sander or planer and sand down those places
until it closes? Then should I stain and waterproof (or laquer it) or
will that trap the moisture inside? Also, if I sand it down, won't it
shrink back to normal size in the summer, leaving me with gaps? I
assume the reason for the swelling of the door is the rain we've
received in San Francisco in the last few weeks.

Thanks!