Are future bonuses and salaries considered unlawful due to lying in a major-specific interview, knowing that there are those with lower grades who were admitted to the same major?

If you perform the work entrusted to you as required, then there is no sin upon you in it, nor in the money you earn from it. Disregard these whispers and seek forgiveness from Allah for your lie to the examiner that your sister has asthma. However, that does not affect the permissibility of your work, nor what you earn from it, if you perform it as required. Beware of whispers, for they are from Satan.