Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concern.
As per your complain and presentation of symptoms  it seems that the 
sinus infection is not yet cured completely leading to bad odour as bacteria and debris present in mucous will cause foul odour..
You need to consult an Otolaryngologist and get evaluated and he can also advise you a Nasal 
Endoscopy to be done to rule out for any polyp or tumour in the sinus..
You will be advised to take antibiotics, anti-allergics like 
Benadryl , decongestants lie Sudafed and mucolytics like 
Ambroxol to loosen the mucous..
Doing steam inhalations and saline nasal sprays will help..
Use a humidifier in your room..
Sleep with head slightly raised so that the sinus can drain..
In case if endoscopy shows any tumour or polyp in the sinus 
surgical treatment has to be done for removal..
At times draining the sinus also needs surgical intervention..
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora.