There are hundreds of types of fungi.
The large majority are beneficial. Some break down dead wood. Others live in close relationships with other living plants, and actually help to nourish the plants they live with.
There are a very small number of fungi that are harmful, and can kill living trees. The best known fungus of this type is honey fungus. But that's only one fungus among hundreds.
You ought to verify that the fungus you have is not honey fungus. And provided that it is not, then just leave it alone.
If you were to post a photo, we might be able to say what type of fungus yours is.