We can't tell the size of the hole from your photo, but it is likely to be from a woodpecker or other wildlife that nests and raises young in tree cavities. Sometimes woodpeckers even begin holes in different places before choosing one to actually use.
It is not going to hurt your tree and there is nothing that you need to to repair it.
Keep an eye on it this spring and you may be treated to seeing a family raised there.


Christine