Vomiting (or, at least feeling nauseous) shortly after a meal can be a sign of:
a) food poisoning ;
b) gastritis (which, in turn, could be caused by an H. pylori infection or excessive use of alcohol or some types of pain-killers) ; or
c) a stomach ulcer.
I agree with electrochem.....gall bladder problem comes to mind.
Monitor the situation and if you feel bloated and "full" after only eating a small amount of food, then avoid fatty foods and see your GP.