He had to be prepared to pay support by even attempting contact at this point.
My advice is to not bring it up at this moment. You've gone without it this long. Let him and his family come to visit yours and work into a slow process of the son and the father getting to know each other.
This could end up being a very supportive and nurturing opportunity for both families. Kind of like a very extended family.
When the opportunity presents itself you can talk to him about the needs your son has. Perhaps he could start picking things up that your son needs. Maybe he pays all the school clothes, sports activities, school luches, etc in exchange for child support. Maybe he offers to pay a certain amount each month because it's easier for him that way.
Just try and keep the courts and the state out of it if at all possible. That only leads to hard feelings and power struggles.
If things don't work out so well, then of course you can file a court petition.