What will happen if food gets stuck in the hole of your tongue piercing?

Any food that remains in your mouth, whether it is caught in the hole of your tongue piercing, or between your teeth, or anywhere else in your mouth, will decay, and will therefore cause a great increase in the amount of bacteria in your mouth, which can lead to tooth decay, or to the inflammation of your gums, or to various other problems. Never let food remain in your mouth for any prolonged period of time.

Of all the parts of your body that you might choose to pierce, the tongue is the most risky, in terms of possible medical problems. I honestly would have to advise against it.