When using Photoshop it's taking up more than 100GB disk space

This is the Photoshop scratch disk.

Raster image editing moves massive amounts of data around, much more than any RAM you may have installed, and all that data has to go somewhere. So it's written to disk. If there's not enough available space, Photoshop can't operate at all.

By default scratch goes to the system drive, but you can put it anywhere in preferences.

For most serious Photoshop work, 500 GB should be considered a practical minimum. If you work on really large files, you may need a TB or more.

The scratch file is vastly bigger than nominal file sizes of open files. It contains all history states for all open documents, and if you work with smart objects there's considerable overhead as well.

As a temporary measure until you get more disk space, reduce the number of history states. This will also reduce the size of the scratch file.