I did root canal. My first sitting was on 2 days ago. Doctor gave me hifenac p for pain. But o took it after one day. But the problem is last day when I woke up I find a red rash on my neck. And I am having pain also in my neck and feeling hot there. Now I read on the medicine that some reactions can be heppand by tacking this medicine. Like rashes hand swelling and illness. But the rash on my neck is done before I took this medicine. So now should I take this medicine or not? And do I have any major problem?