the plastic where your knees off comes out then you should see 2 bolts that hold the column in place, you can try tightening these down.

if you're sure its the wheel, you're gonna have to take out the airbag.... disconnect the power from the battery then there is a plastic piece under the airbag, take that off. under that there is a clip (yellow or red cant remember which) unplug that, thats your airbag power supply... remove the airbag and tighten the nut down.

but i have no idea how that nut could have possibly come loose.