Under the custody statute, there are a list of factors that the court must consider in order to determine whether it is in the child's best interest for you to have primary physical custody and to relocate. You will need to meet with an experienced family attorney to handle this matter because these cases are complicated and there are procedural requirements that you must follow.
My response is based solely on the limited information contained in the question. It is not meant to substitute your attorney's advice.
You will need to send notice to him and his parents if they are parties to the action of your intention to relocate. There are specific items of information that must be included in the notice and you must attach an affidavit for him to complete and file with the court. If he objects a hearing will be necessary. There are 10 factors that a Judge must consider. Among the factors are the reasons for the move, how it will benefit the parent and how it will benefit the child and what arrangements can be made for continuing contact with the other parent.
You should consult with an attorney immediately.