you maybe having an ulser!
You maybe having what is called an aphthous ulcer although i cant tell you for sure without examining you!
If you could take a pic and upload it, it will be very useful!
are benign ulcers and will subside in a few days, you dont have to worry about them!
You can start on hexidine mouth wash and vitamin b complex tablets as they will help in early recovery.
You can also apply mucaine
gel 3-4 times a day on the hole/ulcer it will reduce the pain and help you eat properly.
Meanwhile take rest, avoid hot and spicy food and drink plenty of fluids.