Looks like getting into the kickstart for password recovery has changed a bit with NXOS 7.x. NXOS 7.x features a consolidated binary image rather than the previous pair of kickstart and system images we are used to seeing on Nexus 3000.

It's not exactly obvious how one boots to the kickstart. So here's the new sequence:

Step 1 - Power Cycle and Interrupt to the Loader with CTRL-L

When you see this:

Press  ctrl L to go to loader prompt in 2 secs

Press CTRL-L

Step 2 - Set recoverymode=1 and boot your NXOS 7.x image to get the Kickstart

First, ensure you can find your NXOS 7.x binary image using dir.

loader> dir
...
bootflash:
  nxos.7.0.3.I2.2a.bin

Then force boot to kickstart and boot the image.

loader> cmdline recoverymode=1
loader> boot bootflash:nxos.7.0.3.I2.2a.bin
Booting kickstart image: bootflash:nxos.7.0.3.I2.2a.bin
 Image valid
INIT: version 2.88 booting
Skipping ata_piix for n3k.
...

This should land you at the switch(boot)# prompt and you can follow usual procedures from there.

References

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/6-x/troubleshooting/guide/b_Cisco_Nexus_9000_Series_NX-OS_Troubleshooting_Guide/b_Cisco_Standalone_Series_NX-OS_Troubleshooting_Guide_chapter_01.html

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/password_recovery/b_nx_os_pwr/nx_os_pw.html