yes you should be able to access the flash and delete it
are you in rommon , do you have the below options with delete ? if so you should be able to see the flash contents and then delete the cfg file
ROM Monitor Commands
Enter ? or help at the ROM monitor prompt to display a list of available commands and options, as follows:
alias set and display aliases command
boot boot up an external process
break set/show/clear the breakpoint
confreg configuration register utility
cont continue executing a downloaded image
context display the context of a loaded image
cookie display contents of cookie PROM in hex
copy Copy a file-copy [-b <buffer_size>] <src_file> <dst_file>
delete Delete file(s)-delete <filenames ...>
dir List files in directories-dir <directory>
dis display instruction stream
dnld serial download a program module
format Format a filesystem-format <filessystem>
frame print out a selected stack frame
fsck Check filesystem consistency-fsck <filesystem>
help monitor builtin command help
history monitor command history
meminfo main memory information
mkdir Create dir(s)-mkdir <dirnames ...>
more Concatenate (type) file(s)-cat <filenames ...>
rename Rename a file-rename <old_name> <new_name>
repeat repeat a monitor command
set display the monitor variables
stack produce a stack trace
sync write monitor environment to NVRAM
sysret print out info from last system return
tftpdnld tftp image download
unset unset a monitor variable
xmodem x/ymodem image download
