All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.
If you used to bring him gifts before he received this promotion and there is no fear of favoritism involved, then the most likely correct view – and Allah knows best – is that there is no harm in bringing him a gift after his promotion, nor in his acceptance of this gift, provided that the gift is not more than what you used to bring him before.
As-Subki said in his Fataawa:
“As for the gift offered with the intention of expressing affection or winning a person's heart, if the recipient was not often offered such gifts before holding a position of authority, it is prohibited to accept it. If he was often offered such gifts before holding this position, he should not accept anything beyond the average gifts that were normally offered to him earlier. If the gift-giver is involved in a dispute, it is impermissible for the official to accept his gift (probably presented to influence his judgment or give the gift-giver preference over others). If there is no dispute involved, it is allowed to offer the official a gift proportional to the average gifts that were normally offered to him before holding his position, and it is better for the official to not accept it...”
Hence, you come to know that he did well by refusing to accept the gift, and it is better that you avoid bringing him gifts.
Allah knows best.