ad hoc network in android
As far as I understand your question, you have successfully created an adhoc network on your Nexus and your laptop is able to connect.
Now you want to create an adhoc network on your laptop and you want to connect your Nexus to it.
After doing some research, I've found out that Android does not work (well) with adhoc networks.
There are some custom ROMs which have enabled the Ad Hoc function.From what I've been reading, mako bb-8 and AOKP will be able to do Ad Hocs.I think CyanogenMod has also a modified wpa_supplicant to support Ad Hoc networks.
If you don't want to flash a custom ROM, you could try to rip the wpa_supplicant (from the same Android version you are using) from one of the custom ROMs mentioned before. You could also try to install WiFi Ad Hoc enabler for Android, which might work for you.If that doesn't work, you could try another method, which is harder. Check it out here.

I also found this, I don't think it'll work, but worth mentioning:
http://forum.xda-developers.com/showthread.php?t=1591207