DIAGNOSIS: That gunk is built-up grease and food particles. The 'little hole' is the steam release valve vent, and it absolutely needs to be kept clean to function safely.
FIX: First, make sure the unit is completely cool and unplugged. The silicone steam release valve cap pops off—gently pull it straight up. Soak it in warm, soapy water. Now, for the vent tube it sits on: use a pipe cleaner, a damp cotton swab, or a soft-bristled brush (a clean toothbrush works) to gently scrub inside. Wipe the entire inside of the lid with a damp cloth. Let everything dry completely before popping the cap back on.
IF THAT DIDN'T WORK: For stubborn, baked-on residue, make a paste of baking soda and water, apply it to the vent area, let it sit for 15 minutes, then scrub gently with your brush and rinse.
HEADS UP: Never submerge the main lid unit in water. The electronic components for the lid lock are in there. Just wipe it clean.