What Causes Left Sided Pain In The Neck And Headache Post A Workout?

Hi, 6 days ago I did a new workout video that wasn't very strenuous and was only 30 minutes but for the rest of the day I felt lightheaded, dizzy and weak. I increased my water intake and ate some salty foods hoping that would help but it did not. Since then I have felt increasingly worse. I've begun having a throbbing pain in the left side of my neck that is spreading down to my shoulder and up to my ear. I have had a stabbing headache for 4 days that is also getting worse as well. It began on the left top side and now my whole head hurts. I'm also experiencing flashes of light when I close my eyes. I had an EKG at Urgent Care the other day and it was perfectly normal. I'm concerned it could be related to my carotid artery. Thanks.