Hi and thanks for the query,
It would be interesting to know if the pimple appears exactly where it appeared last time or not, and whether it presents in exactly the same way. The anti biotic might have been effective and y chance, the pimple reappeared, or may be the treatment duration or anti biotic choice was in appropriate and the infection was not completely cleared. Other predisposing conditions around this area that favours this condition should also be sought.
Taking an appointmnent for a reevaluation by your primary care
physician to me is a reasonable option.
Thanks and best regards,