This may be a manifestation of some local trauma
, like a Blood blister
or rarely a manifestation of a mild viral infection
I would recommend observation for a week more since it is likely to improve spontaneously in this time frame.
If not then you could show the same to your physician / dentist for further evaluation
Please remember to accept the answer by pressing the GREEN accept button, do get back for any clarifications
Ok but it's not in a position were i could bite it and I don't remember burning it as it is underneath my tongue