I can't think of a think you can do with soured milk. I'd throw it away without a blink!
Dave's right - biscuits use soured milk (and if you don't have it, you just use regular milk with either lemon juice or white vinegar in it)
Please throw it away. It has bad organisms in it.
If you have a recipe that calls for sour milk, you just add a little vinegar to the milk. Isn't that right, GB?