One must not go to Pillaiyar temple after Bharanyasam.
The absolute things one must avoid after Bharanyasam are
Worshipping other gods and demigods
Offending Bhagavatas
There is no need to despair if you do not celebrate Pillaiyar chaturthi as no harm shall befall. Emperuman is the Lord of all gods. We performed Bharanyasam by having total faith that he will protect us. Bharanyasam is like upholding the virtue of being a chaste wife so one should be devoted to Emperuman alone.