Adjusting areas selected by magic wand tool

This is probably a very basic Photoshop question, but I couldn't remember how to do it and tried several things, none of which worked. I had a picture of a person standing on a white floor with a white background, and I was using a technique I've used in the past to blend the white floor and background to look seamless. Using the magic wand tool and holding the shift key, I select an area on the background and the floor. It did a good job selecting all around my subject EXCEPT for the white socks. Like half of the white socks on both feet were included in the selected area. I wanted to move the selection to the boundaries of the feet so they wouldn't be included, but nothing worked that I tried. I'm sure it's something simple! Thanks.

change the tolerance

What if the colors are almost exactly the same? Is there a way to manually adjust the selected area after it has been selected?

Hit "Q" for quick mask, then use an airbrush to add / subtract to the quick mask. When done, hit "Q" again.

If you have person in white socks standing on a white floor why use the Lasso tool? The Color Range command or the Pen tool will give you a much better selection of the socks.

One option is to save the selection you've already made; use the pen tool to make a selection of the feet, then use the CTRL+Shift keys to combine the two selections.