Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concern..
As per your complain pain in the left corner of the cheek that is painful and swollen can be due to burning with any hot foods, chemical substances while can also be due to cheek bite an bite ca at times be not visible due to swelling..
Nothing to worry as it does not seems to be anything serious and pain and swelling seems to be due to inflammation and nothing serious..
It can however gradually transform into a
canker sore that can heal gradually..
As of now you should apply numbing gel containing Lignocaine over the sore and swollen area.
Give
tylenol or
Ibuprofen to relieve pain and inflammation..
You can do cool compresses..
You can give her a light diet and plenty of cool water..
In case if it still does not improve you should consult a Pedodontist and get evaluated..
Hope this helps..
Regards