I have inherited chronic gastritis and take meds every day for it.. some get headaches, I get acid drip instead. Nicotine, no matter how you get it, smokes, chew, pills, patches or vaping causes acid drip in the stomach as well as acid ooze from the lining... there are two different acid systems to digest food and nicotine affects both of them. I'm sure you got the same stomache if you ever smoked too much. Lower your nic or start taking something like prilosec (I'm not a doc and not advising you medically.) You may have to take prilosec anyway for a few days to give your stomach a break and give it time to heal. In the meantime, stay away from spicey foods/drink including hot ones and cinammon, stay away from acid foods/drink like citrus as these will irritate an already raw stomach lining. Also, stay away from caffeine for a while as it does the same thing nicotine does... increases acid in the stomach... it just takes more of it.
PS: you may not think decaf tea or coffee are a problem while your stomach heals but they are. They both contain acid as potent as any citrus drink or food... so I wouldn't, for instance, replace sodas (acid) with iced tea for instance. These are just measures to take to give your stomach a break since its already inflammed from too much nic.