Changing the audio input in GarageBand on ipad

Help!!! I love GarageBand and use it all the time. Tonight I plugged in some headphones with a microphone into my iPad, and it automatically changed the audio input to the headset microphone. No problem, I thought. Except I have found no way to manually change it back to the iPad’s microphone, and it won’t automatically change back when I use my typical headphones without a mic. Now, with those in, I can’t record anything at all. Any solution? Please, please help.