Chocolate is very poisonous to dogs but luckily, yours ate candy with only a chocolate coating. I will list below how much milk chocolate is poisonous to dogs and you can determine how much chocolate your dog ate and how much he ate. I will also list symptoms to look for in case he did eat too much.
Milk chocolate: 1 ounce per pound of body weight. Approximately one pound of milk chocolate is poisonous to a 20-pound dog; one-half pound for a 10-pound dog. The average chocolate bar contains 2 to 3 ounces of milk chocolate. It would take 2-3 candy bars to poison a 10 pound dog. Semi-sweet chocolate has a similar toxic level.
Symptoms of Chocolate Dog Ingestion and Poisoning
You can recognize that your dog has eaten a toxic dose of chocolate from the symptoms. Within the first few hours, the evidence includes vomiting, diarrhea or hyperactivity. As time passes and there's increased absorption of the toxic substance, you'll see an increase in the dog's heart rate, which can cause arrhythmia, restlessness, hyperactivity, muscle twitching, increased urination or excessive panting.
This can lead to hyperthermia, muscle tremors, seizures, coma and even death.
I don't think you have to worry but, this is good information to have in case this ever happens again. If your dog shows any of these symptoms, take him to the vet right away.
Long time dog owner