I'm very sorry this happened to you and you chicken. Unfortunately, we all make mistakes and have to learn from it. When it comes to chickens, it's even harder since informations about them are not easy to be found. BYC is one of the most reliable sources, but you still need to do research about...
Here is a great article about how to give chicken meds and it also shows the picture of the hole leading to trachea:
https://www.backyardchickens.com/articles/safely-administering-oral-medications-to-all-poultry-and-waterfowl.73335/