Salmonella food poisoning that gets to the point of becoming salmonellosis can give you acute pancreatitis. This is often felt in the upper abdomen, by the sternum (the place you’re supposed to find to give CPR compressions), and then in the back and lower abdomen. It can become a constant ache that refuses to go away, and eating could cause the pain to get worse in some cases. Constant pain is a sign you need to seek medical attention for pancreatitis - whether caused by salmonella or not.
Other symptoms of pancreatitis to be aware of and to watch for if you suspect salmonella poisoning has given you this problem include jaundice, a fever of around 100.4 degrees or more, and even vomiting. These last two are common symptoms of food poisoning in general. If you’re concerned, see a doctor.