Yes. This fits into the Veterinary Medical Emergency category and he should be seen by an emergency veterinary service.
Since he is a large dog he may get away with only gastrointestinal distress, such as vomiting, diarrhea, nausea, and inappetance for a couple of days. But if it was a toxic dose he could end up with seizures and kidney damage that may be permanent.
The toxic dose depends on the percentage of chocolate in the candy. Milk Chocolate can be as low as 25% chocolate, which of course is less toxic. Bakers, unsweetened chocolate is 90 to 100% chocolate and is deadly in very low doses.
Thank You for your fast response. He has shown no sign of illness but my son is calling his Vet. Thanks again....