Taking Doxycycline For A Skin Rash On The Face, Has

Taking doxycycline for a skin rash on the face, has notice or felt pressure around my nose and sensitivity to my front tooth, went to the dentist yesterday did x-rays no cavities , but said that I needed a root canal . Is that possible . I'VE had the rash for a couple of months, been taking the antibodies for about a month .