Deleting Photos Library

In order to free up disk space on my laptop, I set my Photos Library to be stored on my external hard drive. I managed to successfully do this, and after doing this, I went in to my finder and deleted the "Photos Library" or PhotosLibrary.photoslibrary file that was stored ON MY MAC and only left the one stored on my external disk.

After doing this, I opened up my storage management and I saw that my Photo Library still consumed the original 43GB it took up before deleting the file. When I unplug my external hard drive, it says my photos library takes 0KB of memory on my internal disk space, but the "System" tab now takes up an additional 43 GB such that the space available on my mac is the exact same as before deleting it.

How can I delete the memory this Photos Library took up?

Thanks for your help.