You better get an attorney and disclose everything to your attorney ASAP. Perhaps the attorney will still have time to substitute his/her name as your counsel. Your post does not describe anything as regards a timeframe. Anyway, if that works, perhaps your new attorney can make a motion on your behalf to withdraw the plea. If you are before sentencing perhaps you can ask to postpone the sentencing until your new counsel can be there to make the motion to withdraw your no contest plea on your behalf.
Without a lot more details no further observation is possible.
Good luck to you.
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Most municipal court judges will allow you to withdraw your plea, but the longer you wait to file this motion (or have a lawyer file this motion on your behalf) the less likely it becomes that you can get this done. Talk to a criminal defense lawyer who does some municipal court work ASAP.