Yes, Easter is long gone, but chocolate toxicity is still a common enough occurrence in dogs that a link here to a chocolate toxicity calculator could be very useful, It will predict the symptoms (if any) based on the likely volume of chocolate eaten for the bodyweight of the dog, and the type of chocolate eaten.
Pancreatitis, vomiting, diarrhoea and abdominal pain are just the beginning of this disaster. The fat and sugar in chocolate can create an unpleasant but temporary upset stomach in the majority of chocolate ingestion cases. The fat in chocolate can also cause pancreatitis which may require hospitalisation and intravenous fluids to treat.
The nastier ingredient in chocolate is theobromine which is in higher concentration in baking chocolate and dark chocolate. Theobromine toxicity signs include hyperactivity and tremors, seizures, and abnormal heart rhythms. It can be fatal if enough chocolate is eaten.
So, if the calculator predicts that symptoms will be likely for your pet, then the sooner your pet is presented to us then the better the outcome. It may be as simple as inducing vomiting to expel the poison from the body, if timely enough.