Also, those with cancer / recent cancer are at risk of blood clots. You could well have a pulmonary embolus - a clot in the lung vasculature. This is usually sharp and sudden and occurs on inspiration when you take a breath. Some experience shortness of breath with this, however, some do not.This is all very good reason to be checked out.
Hope all turns out to be nothing, but best to get anything unusual checked out.
Tammy

Caregiver/advocate to Husband Kris age 59@ diagnosis
DX Dec '10 SCC BOT T4aN2bM0 HPV+ve.Cisplatin x3 35 IMRT.
PET 6/11 clear.
R) level 2-4 neck dissection 8/1/11 to remove residual node - necrotic with NED
Feb '12 Ca back.. 3/8/12 total glossectomy/laryngectomy/bilat neck dissection/partial pharyngectomy etc. clear margins. All nodes negative for disease. PEG in.
March 2017 - 5 years disease free. Woohoo!