Kindly mention the duration of symptoms. Also, let me know if it is the first time or how did it start. If it is the first time and started following water entry into the ear, it is likely to be a fungal infection. In that case you need to get the ear cleaned by an ent doctor and use antifungal ear drops. It could also be a furuncle in the ear which would warrant a local ointment application and oral antibiotic and antiinflammatory medication.