Hello, Our 17 Year Old Daughter Swallowed A Plum Pit

Hello, our 17 year old daughter swallowed a plum pit on Monday 6 days ago. Since then she became sick Thursday with what we thought might be food poisoning after eating sushi. It's now Sunday and she begins to feel better and eats which makes her stomach feel queasy and upset. She's had little to no fever but isn't back to normal yet. Is this just a stomach flu?