Hello there ,
Thanks for writing your query,
According to your clinical history i suspect you have developed an fluid filled blister or a boil filled with abscess near the lip mucosa .
It is caused may be due to physical trauma , chemical injury to the palatal mucosa or allergy to certain food products , hot or cold injury
to the oral mucosa
It can be viral infection as well , i would suggest you to consult a dentist
and get the examination done.
i would suggest you to go for symptomatic treatment at home like gargling with lukewarm saline water or antiseptic mouthwash like chlorhexidine
Apply oral antiseptic ,analgesic
ointments like dentogel or mucogel topically over the affected area.
i hope this helps ,