You could try to handle this yourself, but that would be a very poor choice because if you did, you would almost certainly lose. You do not know the law or how to prosecute or defend a civil action in court and your adversary, since he is a lawyer, presumably does know these things. That superior knowledge would give him an essentially insurmountable advantage over you.
Depending on facts you do not state, the lawyer's lien may or may not be valid. The only way to test it is to challenge it in court. There is also a legal way to try to stop foreclosure of the purported lien and a legal way to stop the sale of the house. To pursue any of these things with any hope of success, however, you must hire a lawyer who knows what to do and how to do it.
Mr. Karotkin has given you an excellent answer. You need to hire an attorney to evaluate the lien agreement, fee agreement, and "all the facts". You should take such an action ASAP. Do not wait for the attorney to try and "foreclose" on his "lien" or to fight about the lien when you try and sell the property. It also appears you may also need an attorney to further prosecute whatever the claim is that gives rise to the original contingent fee agreement, if that claim has not been completely resolved.
You need to consult another attorney ASAP.
I would recommend you hire an attorney who is Board Certified in Civil Trial Law.
This answer does not constitute legal advice or create an attorney-client relationship.