Hello and thank you for using this site to help you.
Items like sausage which are considered fatty can actually cause pancreatitis so you will want to avoid such foods. Usually with this we see fever , lethargy, vomiting, diarrhea.
Pancreatitis in some cases needs hospitalization.
At 8 weeks old he is not fully vaccinated against the parvo disease so that is always something to keep in your mind and watch for symptoms of that as well.
If he eats any non food items such as rawhides, greenies, bones, etc. then you have tow worry about an obstruction of the bowel. This would show lack of appetite, change in stool or stool habits, lethargy , and vomiting. A blockage would require surgery.
It possible that the sausage did give him a bit of upset stomach so for now keep an eye on him and do not feed him anything for 24 hours then start a bland diet of boiled chicken (no fat, skin , grease) and cooked white rice. The fasting and the bland diet will give him the time needed for the intestines to calm down.
I am going to direct you to a link on how to take the vital signs of a dog and I would certainly want to keep an eye on the gum color, capillary refill and temperature.