Whether there is potential for a re-trial depends on the local criminal procedure law. In some jurisdictions, the prosecutor has the discretion to begin again, but in other jurisdictions, the prosecutor has to convince a judge to allow the re-trial to go ahead. So a juror nullifying may make a re-trial difficult to get.
As well, a re-trial is only an option if nullification leads to a mistrial. However, if the jury unanimously agreed to nullify and renders a verdict of “not guilty” (as happened in the Emmett Till case), there’s no chance for a re-trial (in the US).