Funny this topic is created because umm...lol. I made a mistake.
I have both an iPhone 5 and Nexus 4 and I go back and forth...well, last week, I wasn't paying attention and took my sim out of my Nexus 4 (I have a adapter for the Nano sim to fit in the Nexus 4) and made the HUGE mistake of putting the adapter and sim tray back in the Nexus without the Sim Card in it...soooooo...my Sim Tray got stuck in the Nexus 4 because the Sim Card wasn't in it...ultimately, my Nexus broke and I had to call Google and order a replacement Nexus 4.
So, DO NOT put the adapter in the Nexus 4 Sim Tray and put it back in the phone WITHOUT the nano SIM card in the adapter, because it will get stuck and your Nexus 4 will mess up. If you put the Sim Tray back in, make sure the adapter isn't in it as well.
Luckily, Google gave me a free Nexus 4 replacement after I explained what happened.