HI I read your mail as you said you are average smoker till last week and you are noticing blood in your sputum for one week,you feel as something is trickling at the back of your nose to your throat but no blood is seen in nasal discharge on blowing your nose for cleaning,this story brings some fact in my mind that you may be having some pathology in your pharynx which extends from back of nose to larynx
& opening of oesophagus(food canal),to clear this you should be examined by E.N.T.specialist for diagnostic nasal endoscopy
and Direct laryngoscopy
to findout the site of bleeding.you should also go for culture & sensitivity of your sputum,sputum for AFB,X-Ray chest,X-Ray paranasal sinuses
.After above exercise i hope your problum will solve and one can get the correct line of treatment.Thanks.