Hi..
Welcome to HEALTHCARE MAGIC..
So sorry to hear about your problem and will try my level best to resolve it to the best of my knowledge..
As per your explanation a painless, hard, quarter sized lump on the roof of mouth can be due to formation of a Palatine torus that is a nodular overgrowth of palatine bone and although it may cause discomfort but it is harmless..
Other cause can be due to formation of
mucous cyst or
Mucocele that occurs due to either ruptured duct of minor
salivary gland or obstruction in the duct or its gland leading to a painless and harmless lump..
Consult an Oral Physician or an Oral Surgeon and get evaluated and a thorough clinical evaluation and
x ray can help in confirmation..
In case of palatine torus surgical removal of overgrown bone can help..
In case of mucocele you can be advised to gargle with concentrated salt water and if it still does not regress surgical excision can be done for resolution..
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora.