Brief Answer:
Information about associated symptoms would help

Detailed Answer:
HI XXXXXXX
Thanks for your query.
Sudden ear pain can be due to problem in ear itself...like bold cleaning of ear ,trying to remove wax vigerously/ building of water in middle ear..(otitis media ) with infection.
Other associated complaints ..allergy with sinus,blockage of eustachian tube followed by forceful blowing of nose/Toncilitis or pharyngitis along with throat pain./Tooth problem causing reffered pain in ear/Temperomamdibular joint pain due to arthritis,wide opening of mouth like when broad yawning/biting hard big object forcefully.
So to pin point the cause more details of associated problems is essential.to enable me in to be more specific in answering.
An ENT specialist can find it out after detailed check up,in case you can not find one.This would help in advising more specifically for effective management.
I hope that helps you.Any follow up query is welcome.
Thanks

---