Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain foul smell from nose that exaggerates on changing position like looking down or up along with headache seems most probably be due to infection in sinus also known as SINUSITIS.. As the sinuses drain through nose you are experiencing foul smell in nostrils.. I would suggest you to consult an Otolaryngologist and get evaluated and he can do a clinical examination and also advise you investigations like Nasal endoscopy, PNS view x ray of sinuses and/or MRI SCAN to rule out the exact cause and treat accordingly.. In case if Sinusitis is confirmed as the cause you can be advised to take a course of antibiotics, anti inflammatory painkiller, decongestant, anti allergics, saline nasal irrigation, steam inhalation and steroid nasal spray.. You can also be advised to avoid chilled foods and air conditioned atmosphere.. As of now you can do saline nasal irrigation, take steam inhalation with few drops of Eucalyptus oil in boiling water.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.