the Fatwa Department Research Committee - chaired by Sheikh `Abd al-Wahhâb al-Turayrî
If you can find it in your heart to forgive that person, it would be of great benefit to you. However, it is not obligatory on you to forgive a person if that person has wronged you and refuses to make amends by restoring to you your rights.
However, you should not be unjust to him or refuse to greet him.
It was related in our history that `Umar b. al-Khattâb never reconciled himself with the man who killed his brother Zayd, even after that man accepted Islam. At the same time, this dislike on `Umar's part did not cause `Umar to treat that man harshly or deprive him of any of his rights.
Nonetheless, you should keep in mind Allah’s saying: “Those who spend (freely) whether in prosperity, or in adversity; who restrain their anger, and pardon people; for Allah loves those who do good.” [Sûrah Al-`Imrân: 134]
Source: Islam Today