Hi: please read the Governing documents of your HOA and seek legal advise. If the special assessment is allowed, according to the Governing documents, there may not be anything you can do but pay them. The association probably has the right to place a Lien on your home and probably collection fees, etc. I do not know the particulars of your situation, but you should seek guidance before they start collection proceedings.
It is pretty amazing the power the HOA's have on people properties. I am a Realtor in Florida and they can put liens here. Call the Legal Aid Society for help or a local Real Estate lawyer for NJ laws and see if they can help. Best of luck to you.