Do you and the father live together?
If the father claimed Head of Household and claimed the child as a dependent, then he already claimed all the possible tax benefits for the child. Please remove the child from your return altogether.
In the case of parents who live together with a child, one parent claims every possible benefit for the child (the parent with the higher income). The other parent doesn't list the child at all. Only the rules for divorced or separated parents allow the benefits to be on 2 tax returns.
If you don't live with the father, who has primary custody of the child?