Such a rough way to start off vaping!
I had a friend who was sensitive to some of the flavoring agents. A few liquids she could vape fine, most not. Most caused her tongue to get sore or even raw and sometimes a liquid would cause it to start to swell up.
She had to use process of elimination (along with many a day of discomfort with a new liquid and $$$ spent on bottles that she practically gave away on the classifieds) to figure it out liquids she could vape and it took a long time to just find liquids she could vape. She never did identify exactly what it was.
Some of the (common flavoring) ingredients and normal components in e-liquid you would find could be:
Tobacco essencial, tobacco leaf oil, Nicotine (from tobacco leaf), Trimethylpyrazine, Tetramethylpyrazine, Dimethylpyrazine, Acetypyrazine, Methyl butyric acid, Terp ineol, Ethyl maltol, Guaiacol, Acetyl pyridine, Octalactone (gamma), Pure water, Propylene Glycol, Glycerol (from a lab list of Totally Wicked ESmoking Liquid)
Any of the above could potentially cause a reaction.
One way to try to figure out if it's a flavoring agent is to vape only PG in a new/clean atomizer/tank/carto. Then try VG. If those don't bother you, introduce the nicotine into either one. If you can vape those without discomfort, then it definitely is a flavoring ingredient and you'll have to stick with sample bottles until you can find one that you can vape or DIY your own so you know what is in it.
Good luck (and keep us updated!).