Get a lawyer in your own country to sort out the legal custody of your child. CIC will want something from the father stating he is allowing the child to leave. If you can't find him, you will have to prove that you seriously tried to find him, could not, and that you have sole custody.
If you do find him, and he refuses to give permission to let the child leave, you can still take the child, but it will be more complicated of course.