Welcome in H.C.M.
I have gone through your query regarding bump on throat, does not hurt and giving dark phlegm.
After analysing and co-relating your symptoms it appears as you are suffering from chronic tonsillitis
. The bump you have seen is most likely enlarged tonsil and this may give rise to recurrent pharyngeal infection thus you may get dark phlegm.
To confirm this possibility you may consult your ENT doctor for clinical examination and investigation to confirm the diagnosis and relevent treatment.