I get a partial blockage in my parotid (spit) gland, situated in that exact spot. I have a condition called Sjogren's Syndrome which results in vastly decreased saliva and also tears. As a result of this, the solids in saliva become more concentrated and form small gritty stones which get blocked in the salivary duct leading from the parotid gland to the mouth. When this happens, I get a severe, sharp pain on the side of my jaw, and the gland swells up. After the grit moves, it clears up. Perhaps something similar is happening with you, but worth getting checked up just the same.