Change the GFX used by those parts back to how they originally were.
If that would screw anything else up, change the tiles used by the other things.
Hm... it would mess up other stuff. So how do I open up the border in the OW editor, so I can change the tiles?
I don't think the overworld editor has that option.
I've had this problem many times, when you were editing the GFX for the title screen, you used tiles that were the part of the border of the OW.
In order to fix that, you must return the GFX back into their place, it is located by the GFX for "Super Mario World"I wonder what a HFD opcode would do in ASM...
Uncheck "Use Joined Graphics" in the Lunar Magic options and then extract the GFX files with the red mushroom icon. This will make a separate file for each section of graphics in the graphics folder. In yy-chr, open the one titled GFX29.bin. View it in GB mode. Banks 54, 54 and 56 are where the overworld border graphics are located (You can see which bank by mousing over the main graphics area, and it will display in the line below the graphics window).
Now set your edit window to 16x so my instructions will make sense. I'll go in order bank by bank and tell you want needs to be in each one. There are three colors to work with. White (W), Light Gray (L) and Dark Gray (D). For each letter I post below, put that color in each square on the edit window. It won't line up right on the forum thread, so just count.
For bank 54: Should look like a white square with a dark gray edge around the top and right side, and a light gray edge under that