Remove filler from drywall edge transition

[AmatörAmanda]

I've messed up. I was trying to be "nice" and help my guy with plastering while he's been away. The result is so bad that I need to somehow remove it from one of the gypsum seams. How do I do it??? Sanding, which is the method I'm trying now, is hardly working, and the gypsum rasp doesn't work either. I can't replace the board either. Anyone have any ideas?

 

[etompau]

If you're not going to remove the disc, then sanding with appropriate equipment is needed.
Sandpaper on a block or a small sander perhaps?

Take a picture of your work for more advice.

 

[AmatörAmanda]

Okay, thanks. I'll keep struggling then.