Your question doesn't say so but I assume that you were served with a summons from the condominium association for past due assessments. Assuming it is a typical case, the condominium association lawsuit is probably for foreclosure and/or for the money damages.
Regarding what to do next, read your summons carefully about responding to the complaint and the time limitations. You should also consider contacting the lawyer representing the condominium association. There may be other strategies depending on the facts of your case. You should contact a lawyer.
Just like you promised the bank to make your mortgage payments, you promised the HOA to pay their assessments when you accepted the deed to your house. If you don't pay your HOA dues, they can file a lien and foreclose it like a mortgage.
If you cannot afford to make your mortgage payments or pay your HOA dues, you may be able to get some relief in bankruptcy. You should consult a bankruptcy lawyer in your area about your options in this case.
Disclaimer: This answer is provided for informational purposes only, does not constitute legal advice, and does not create an attorney-client relationship. Actual legal advice can only be provided after completing a comprehensive consultation in which all of the relevant facts are discussed and reviewed.
My advice is do something. With the HOA, about all you can do is negotiate with them. As far as the bank, you need to defend the foreclosure. Bankrutpcy is the last resort in my opinion but sometimes its the only thing one can do. If a defense attorney looks at your foreclosure from the bank and says there is no way to fight it, or its too expensive to fight it AND the HOA will not budge and negotiate, then Bankrutpcy becomes that last resort. Fighting a foreclosure somtimes permits a loan modifcation if you have income ,or a short sale, deed in lieu. The end goal is at a MINIMUM is to not get a deficiency judgment from the bank that will follow you around for years to come. That is the minium. You may get that minimum from Defending or filing bankrutpcy.