hello and welcome to HCM forum,
i would like to inform you that the opening which is now present on your chin is called a sinus(opening),
i would strongly recommend you to see an endodontist(RCT specialist) as the root canal treatment
has to be redone.
The infection in the tooth has now spread to the surrounding areas,therefore the swelling appeared.
taking antibiotics alone will not resolve infection, therefore kindly visit a dentist
i hope i answered your query,
i wish you good health,