There are two related issues here. First, there was a job resignation that related to a person (you, I assume?) resigning their job under alleged duress from the company. Second, there is a smell and/or hygiene issue.
When you voluntarily resign a job, typically a company will request some kind of resignation letter from you or at least a signed form so that it can later prove that the employee quit voluntarily, if needed. Only you know whether you submitted this type of documentation and/or at least made verbal statements to your management or coworkers about why you were leaving. You may or may not have also participated in an exit interview. If so, I hope you were honest that conditions had become intolerable (or you at least you didn't give statements that contradicted the real reason you left).
At the heart of the matter is why you are alleged to be smelling poorly. You probably have some idea whether it's actually true or not based on others' reactions to you. Think of past scenarios and other settings. Has anyone else even hinted that you didn't smell good or is it just this employer?
If you do smell poorly, do you have a medical condition that would explain this? Is the reason instead related to your cultural or religious practices that the employer was being insensitive to, or are there illegal biases against you such as race, national origin, religion, etc.?
You indicate that your former employer nagged you to quit. I assume that there was a pattern of aggressive, escalating behavior towards you that resulted in you finally giving up and resigning. Before doing so, did you at least try to talk to someone in HR about it or complain about the behavior? I hope so.
Unfortunately, it will likely be an uphill battle. You might want to start with immediately filing an unemployment claim with your state unemployment office disputing that you voluntarily quit.