Pain in the stomach that disappears after eating food can due to an ulcer. There are different types of peptic ulcers - pain from gastric ulcers is aggravated by food and duodenal ulcer pain subsides after eating food.
If you had some mild erosion of the mucosa of the stomach or duodenum prior to the onset of the kidney stone and if you were treated with painkillers, it is possible that the gastric irritation caused by the painkillers and other medications may have contributed to the development or aggravation of the ulcer.
You will need evaluation by your GP and treatment for an ulcer, if it is confirmed. In the meantime, you can start taking ranitidine (zintac/rantac) 150 mg 30 min after a meal, twice daily. Also remember to have small meals more frequently - every 2-3 hours, avoid spicy foods, caffeine, and alcohol, and add plenty of fiber to diet.
Do keep us posted on your doubts and progress.