HI there... okay I am going to go against the flow here. I don't want you to worry - however you should have it biopsied asap. I am saying this for two reasons. Firstly the sooner you know the better it will be. Assuming it's nothing (which is entirely possible) knowing sooner will put your mind at ease. Secondly, the previous lesions you've had (the ones that have been there a while, could very well be nothing). The tender one - as your dentist said - should be looked at. And in my opinion the sooner the better. So I would push to get in before hand, have the biopsy done - do your exams and forget about it until the results come back.
See my sig line - this will somewhat explain why I am pushing you to deal with it now. hugs and best of luck. PS if nothing else please call the person doing the biopsy and ask to be put on a waiting list. That way if there is a cancellation - they will call you. take care.