What will happen if I go around my attorney and settle my case with the other side for less?

Any settlement check is going to have the lawyer's name on it, as he no doubt has notified them of his lien. He will get his share of any settlement.

Your attorney will likely be entitled to a portion of your settlement, depending on what your retainer contract reads. First discuss with your attorney if he is willing to drop his lien and you both part ways. Also, request an accounting of time he has spent on your case. Otherwise, you may want to fire your attorney, and then typically he would be entitled to his hourly work (and costs) spent on your file. Feel free to call another attorney first to review the lower settlement you have in mind.