Actually its impossible to install dsiware to nand without a nand write tool.
However you can still create valid .bin files using system settings from hyja cfw sdnand, you just wont be able to restore these to sysnand without nand access.
First you need a valid tmd for the dsiware title, then you need to create a valid ticket for it too.
Otherwise system settings will not create a .bin file.
(This guide tells you how to create valid tmd and ticket files:
Photo guide to installing DSiWare backups on real hardware and emulator | GBAtemp.net - The Independent Video Game Community)
After that copy the files to sdnand
ticket file goes to: SD:/ticket/00030004/xxxxxxxx.tik
tmd file goes to: SD:/title/00030004/xxxxxxxx/content/title.tmd
(xxxxxxxx are the last 8 digits from your dsiware title id)
Then go to system settings (sdnand)
and create a backup .bin
After that you need to copy the dsiware ticket from sdnand to sysnand using a
nand write tool
Then go to system settings (sysnand)
and restore the backup
(without the ticket in sysnand its impossible to restore the backup .bin, even when its valid. It will throw an error without ticket)