It is not all that uncommon for a dog to get into food that he should not; they can be exceedingly quick at grabbing food off of coffee table or other areas of access.
In most cases, you will want to feed your Chihuahua as normal and try to encourage the ingestion of food as soon as you noticed so that there is more food going through the digestive system than just the cheese.
Depending on the amount that was eaten, the puppy or dog may have some loose stools so you'll want to keep an eye on that. If there is any minor to moderate diarrhea, it will be important to keep your Chihuahua hydrated and this can be done by encouraging the dog to drink water and/or offering Pedialyte which can bring electrolyte levels back to normal. Typically you will want to do a 50/50 mix of Pedialyte and water.
If the dog suffers from severe diarrhea, this should be reported to the veterinarian.