Hi, This statement is bit confusing and thus difficult to imagine a clinical situation depending on it. Tonsils are part of pharynx and are far from gums. However, A fluid filled blister in the mouth that comes and goes can be Mucocele but that happens in and around lips.
Next Steps
Opinion of Specialist ( Oral Maxillofacial Surgeon ) for proper diagnosis and thus rectification is recommended.
Health Tips
Do not ignore even if it is painless.