Carotid Artery is blocked and has a lump, what is this?

My dad had a stroke,8months ago, his right carotid artery was repaired and the left side has a great amount of blockage and could not be repaired. He had a byp at the same time the right side was repaired. His left carotid has developed some pain,swelling and a knot in the area just below the ear. His blood pressure and sugar are under control. What could this be? Another stroke?