What do you think it is? Why do you think it is trying to escape?
I think you will be the only one to answer these questions as they pertain to you specifically. As similar as experiences may be, they all are highly personal experiences.
A couple thoughts..
maybe this symbolizes that you want to speak up or say something and do not. The words want to come out and are not allowed, the words or rather the idea in your mind fights to escape.
Einstein once stated that imagination is everything. I have found that if your mind attunes to something in your experience, that thing you attune to sucks you into a story line, I have referred to this as sideshows a time or two. Perhaps this is just another side show. Move on to the next show. You could also attempt to play with this thing. Imagine giving it an escape route out of your mouth. Perhaps imagining this happening could alleviate this weird sensation in your mouth.
Flummoxed is a very apt word indeed! I am flummoxed myself!
Let us know how this all pans out for you. Wondering if this was a one time occurrence or if something similar repeats itself.
Good luck!
“Silence is a source of Great Strength.” ~Lao Tzu