It's very possible it's a small callous if you do bite the area your body has a way of protecting itself. However the dr. likely referred you for a biopsy and you should go/have gone - maybe reschedule? It is the best and fastest way to ease your mind as it's usually very definitive. An ENT familiar with Oral Cancer is the best choice for you to see, however, your dentist was doing her do diligence by referring you for a biopsy.

Based on the amount of time you've had it with no change I'd say it's probably nothing, but better safe than sorry. We've had young people with no precursors for this disease, diagnosed, and this cancer based on location and size - can be painless. The one thing that makes it sound NOT like cancer would be the amount of time you've had it with no change. Usually at this point it would have gotten bigger, and moved into your nodes, so chances are it's nothing... best of luck