Thanks for writing to H.C.M.
I have gone through your query regarding sharp chest pain
and pink phlegm.
As you said you are a patient of sinusitis
so I cant rule out respiratory tract
infection involving your lung and pleura without examination findings and investigations. Your symptoms are common for both the possibility you are suspecting.
Thus a thorough examination of cardio-respiratory system is necessary along with relevent investigations to confirm the diagnosis for possible treatment and to prevent complications.