Will face pressure and random gum pain subside after having a crown adjusted? the tooth already had a root canal. why is there sinus like pressure?

Possibly: If the problem is due to a poor bite, then yes, you should be fine. If the problem is due to a recurrent infection or a fractured tooth, then those problems will have to be addressed.

Periapical Abscess: If a root canal procedure has been done in the past and it becomes infected again, adjusting crown is a temporary solution. See an endodontist for a root canal re-treatment.