Hi it sounds like an infection and water will not help that.
You have left it far too long so you must call up your Vet if you dont it will keep eating away and it will turn into gangerine so then the out look is grim you must make sure your pig is kept clean and happy at all times she cannot be neglected ever.!!!!!!
It might be a good idea to google care of pigs and thier problems to gain further knowlidge.
I am only replying to the very short question you posted as you give no other details which makes it difficult.
I own a small farm so know a bit about farm animals but you do not say if your pig is farm or pet but my basic advice is sound which everyone should know.If they have a animal of any kind.!!!!
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