hello and welcome to HCM,
some amount of bad smelling discharge is common in sinusitis
which is what causes the sinusitis especially when you bend forward, the infected mucus comes forward and leaks out. This mucus is very smelly. In the same way as and when the mucus becomes a little liquid it tends to flow on to the back of your throat so do not worry about that post nasal drip
Since you have already started on antibiotics then you do not have to worry much. However if the smell persists or the pain increases then you may need further evaluation and treatment and possibly more stronger or injectable medications.
take steam inhalation and take the full course of medications
take care and get well soon
Dr Sriram Nathan