Last Night My Lower Left Jaw Started Hurting, Around 5pm,

last night my lower left jaw started hurting, around 5pm, its now 4pm the next day, still hurts, i didnt hit it or anything, or chew anything hard, or chewy

i dont think its TMJ all of a sudden, i am 50, healthy, not overweight, not high b/p& today i swam 35 laps in pool today, a mile, so when it still hurt i checked on line & it said it was a heart attack symptom....what else could it be, so sudden?