How can i stop coughing?

i keep on coughing because there are small particles in the top of my trachea dont worry they are from something i ate ages ago, i think there embedded in the mucus lining of the trachea.... ive seen some in my sputum but not all of them are coming out, what do i do, ive tried inhaling steam with vapo rub in it and i have tried cough medicines and cough sweets (cough drops, for you yanks)... what can i do? i thought that this was realted to the cold i had for the last week but the cold is gone and the cough keeps goin....is there a medicine that can be perscribed that stops coughing, im asking coz i kno that persistant hiccups can be stopped with an injection of some drug and they're invountary, so maybe there is something to stop an involuntary cough