If one opts not to receive communion pending confession for a mortal sin is it still OK to go to the priest during communion to receive a blessing or should one stay in the pew?
Such an individual should simply remain in prayer in the pew. There is no option in the rubrics of the Mass for a blessing at that time. It should also be noted that a blessing is given to all present that the end of Mass.
As the CDWDS has written:
The liturgical blessing of the Holy Mass is properly given to each and to all at the conclusion of the Mass, just a few moments subsequent to the distribution of Holy Communion.