HR is already involved, or your boss is an complete idiot.
He would/should never have spoken to you about this type
of issue without speaking to HR first...
If he did, he has placed himself in jeopardy.
Filing a counter complaint will get you nothing, it will
be amended to the original complaint and is most often
looked at as antagonistic and defencive.
You do have a right to know who has filed the complaint.
What you cam be assured of, unless your boss is an idiot,
is that there is a written complaint against you now in your file.