Hello, Thanks for writing to HCM , I am Dr Saleha Saeed I have read you question and will guide you through the process of your recovery. You got slapped on the ear this might have caused some damage to your ear drum, I will need some days to heal up, you did not mention any bleeding or hearing loss so i believe damage would be minor but it still would need care and protection from irritation and water. During bath water entered the ear and might have touched the damaged and possibly inflammed area of the ear so it started paining, I would suggest you to protect your ear as much as you can for atleast 10 days , protect if from further trauma, do insert ear buds when you take shower, don t insert anything like Q-Tip etc into your ear, If you find any discharge specially blood and pus coming out immediately contact your doctor. This will take a couple of weeks to get perfectly back to normal. I hope this answered your question.If you have more I am happy to answer. Regards. Dr.Saleha