Suggest Remedy For Irritation In Throat After Swallowing Plastic Piece

My 9 year old son has just swallowed a small plastic duck about the size of a penny. He is now insisting on sticking his fingers down his throat to bring it up. He wants to go to hospital and says he feels poorly but he has global developmental delay and is a bit obsessed by hospitals. Will it just pass through him or should I get him checked out?