Honestly, it could be anything! It definitely could be what you're eating but it also could be any medication you're on, if you're mixing medications, gallbladder problems, acid relux, esophageal problems, stomach problems, food allergies, food bacteria, ANYTHING.
Personally, I would continue to try to eat normally and if it lasts more than a week, make an appointment with your doctor.
I get nauseous almost everytime I eat but I have a great deal of upper GI digestive problems. I try to ignore it and just keep eating as normal. It's when you're throwing up every time you eat that you should see a doctor immediately.