DIAGNOSIS That's the fan motor or the fan blade assembly. Something is either loose and vibrating, or debris got past the filter and is hitting the blades.
FIX Unplug it and let it cool completely. Open the back panel (usually a few screws) to access the fan area. Check for any loose screws on the fan mount. Look for any food bits or packaging material that might have gotten sucked in. Carefully remove any debris. Make sure the fan spins freely by hand.
IF THAT DIDN'T WORK The fan motor bearings might be worn out. You can't really fix that yourself; you'll need to contact Cosori for a replacement part or a repair.
HEADS UP Be gentle when checking the fan blades. They're plastic and can snap. Also, don't run it with the noise continuing—it could cause the motor to fail completely.