Since the return has been filed, you will have to wait for a response from the IRS as to whether the return is Accepted or Rejected.
If your return is Accepted, then you will have to file an Amended return (Form 1040X), BUT you will want to wait until your original tax return is processed by the IRS.
If your return is Rejected, for whatever reason, you will be able to edit your return and enter your son's information prior to resubmitting it.
