you are very active even in this young age!
if the cyst is very hard you can think calc flour too in low potency.there are many types of cysts and most of them are not serious.usually it occur by obstruction of some glands(sebacious,dilatation of acini in thyroid,cogenital,acquired or parasitic etc,etc...).pus will come only when infection occur.usually cyst contains porridge like or tooth paste like matter.please don't touch or pull it always.look for any black dots on it.
so please continue to enjoy life as you are doing now ,and you are a very positive person too.
with regards,
dr jayakumar pannakkal

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