18 month old stuffed potato and egg up her nose. could this cause sinus problems? will it come out naturally?

Maybe/not: Over the years I have had to retrieve beads, pieces of pork,foam, tissue paper, vitamins, rocks, etc. from the nasal passages of kids. The effect on their sinuses if any is short term. Sometimes these kids present as a stinky kid with no obvious issue until you look up their nose. Removal of the foreign body and treatment of the sinus infection clears up the bad BO.