Is it better to expose someone who wronged me and stole my opportunity, or to conceal their actions?

The injustice mentioned in the question is forbidden (haram) because it involves withholding a right from its rightful owner and giving it to someone undeserving out of favoritism. It is permissible to openly declare the evil deed of the oppressor, based on the Almighty's saying: "Allah does not like the public mention of evil except by one who has been wronged." However, it is better for the wronged person to conceal and forgive the oppressor, based on the Prophet's (peace be upon him) saying: "Whoever conceals [the fault of] a Muslim, Allah will conceal his [faults] on the Day of Resurrection," and based on the Almighty's saying: "The recompense for an evil deed is an evil one like it. But whoever pardons and makes reconciliation - his reward is due from Allah."