It depends on what you mean by fully cooked and what kind on fish it is. Parasites in fresh water fish can make a person sick if the fish does not get hot enough to kill them. Parasites in salt water fish cannot live in the human body.
You are at a sushi bar
I don't want to die I just need food poisening :S
Many people eat raw fish - ceviche, sushi, etc. You wil be fine - you have now entered the era of fine dining to many people.