Migration Assistant: I let my new Mac go to sleep and now my keyboard and mouse won't let me input anything. How do I fix this so I can finish the transfer?

Bit more background. Bought a new iMac yesterday (since Apple didn't refresh the line!), and Migration Assistant said my transfer was going to take 5 to 6 hours. I left it going overnight and when I came back to it the computer had powered downand on my source MacBook had said the transfer was complete. When I started it back up it asked me to input my iTunes login info to complete the setup. But, my wireless keyboard and mouse we're no longer connected to the iMac and I couldn't input anything. Any idea how to fix this? Do I just need to buy a wired keyboard?