Blood Blister: If you are sure it's a blood blister: thinning of a blood vessel wall could cause ballooning when the pressure goes up, then collapse when the pressure goes back down. The concern is if this blister doesn't resolve and gets cut, getting it to stop bleeding could be difficult.
This is an old British riddle from 1300-1900 AD. What is the longest and yet shortest thing in the world, The swiftest and yet the slowest, the most divisible and the most extended, The least valued and the most regretted, without which nothing can be done, Which devours everything, however small, and yet opens the life and spirit.
SHAKALSHAS (10 letters) is the longest word which can be typed using only the middle row of letters on the keyboard. Others include HAGGADAHS, FLAGFALLS, HADASSAHS, GALAGALA, GALAHADS, HASKALAH, and ALFALFAS. The only dictionary word which can be typed using only the bottom row of letters is ZZZ (to indicate sleeping). (There are no vowels in the bottom row.) AFTERCATARACTS, TESSERADECADES and TETRASTEARATES (each 14 letters) are the longest words which can be typed using only the fingers of the left hand, using the standard method of typing.