Thanks for putting up your question on Just Answer.
The dizzyness and the head pressure is mostly unrelated to the tooth. The pain however could be due to various reasons. The tooth that has had a root canal could have a re-infection. Or the crown that was made following the root canal could have caused your occlusion (bite) to go askew.
Honestly, without a physical and X rays it is impossible to diagnose what the cause could be. Please see your dentist for the same.
Meanwhile, also see your physician to rule out any sinus issue that could be causing the head pressure.
Till then, switch between taking 400 milligrams of ibuprofen (e.g., 2 tablets of Advil), and 1000 milligrams of acetaminophen (e.g., 2 tablets of extra-strength Tylenol) every 3 hours. Be careful not to use these medications if you have had previous adverse reactions to either, or if you have had gastritis or peptic ulcer disease in the past, or if you have liver disease.
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Good Luck !