Welcome in H.C.M.
I have gone through your query regarding continuous irritation in throat and feeling of some thing obstructing in throat, recently you notice blood in sputum as well.
Considering all about your symptoms and co-relating them with possible pathological lesions in the throat possibilities of cancer is unlikely. most probably you are having any of these-
(gastro esophageal reflex disease).
2- Recurrent Tonsillopharyngitis.
3- Local lesions at the base of tongue.
4- Ulcer at interarytenoid region.
So I would like to suggest you that you should consult any ENT doctor ,who will very easily find out the real disease by doing endoscopy
Need not to worry.