Why you are asking us how? You are the one using the phone. IP68 means the phone is dust proof and water resistant up to 1.5 meters for half hour. It doesn't means your phone is completely water proof. Can you see water inside the camera or just the image taken are blurry?
Don't worry. Take the phone to a service center. Most probably you have to pay them service charge as water damage will not be repaired under warranty. Although its not recommended by professionals, you can try warming up the front camera glass slightly with a hair drier, Don't warm it up continuously. Apply heat at a regular interval till the vapor disappears. Maybe like 5 seconds heating at an interval of 20 seconds. Hope this will help. Keep in mind IP68 is just an additional layer is protection. It can't completely prevent water entry into the phone.
