You took a single antibiotic? Or a course of them? If it is only one, that is not only useless but also breeds antibiotic resistant bacteria.

I'm guessing the bump is a canker sore caused by the dental work. They are usually caused by injury. Canker sores can show up just from biting your cheek or lip. I would call the dentist to make sure, but if it is a canker sore, it should go away on it's own in a couple of days. They have numbing meds over-the-counter at the drugstore that can help, especially when eating.

If it lasts more than a couple of days, go back to your dentist or to the doctor.

it may be reoccrance of infection..go to ent test he vl surely rule out the things