Does a person's admiration for their own work nullify it and diminish its reward? And does Hajj become void if its performer feels pride or admiration for it when people congratulate him? And is there an expiation for that?

Rejoicing in the performance of the obligation of Hajj or other accepted acts of obedience is permissible and does not affect the deed, for Allah Almighty says: "Say: In the bounty of Allah and in His mercy – in that let them rejoice; it is better than what they accumulate" (Quran 10:58). And for the saying of the Prophet, peace and blessings be upon him: "Whoever is pleased by his good deed and displeased by his bad deed is a believer." And "that is the immediate good tidings for the believer." As for blameworthy self-admiration (ʿujb), it is the magnification of one's deed or blessing and relying upon it, while forgetting to attribute that to the Bestower, Glory be to Him.