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, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
You should seek the forgiveness of Allah for the cheating which you committed and sincerely repent to Him by regretting your sin and resolving never to commit it again.
As for the certificate obtained through cheating in the exams and the job and earnings acquired as a result, we have previously highlighted in other fatwas that if a person cheats in the exams, even if he knows about the unlawfulness of cheating, and then finds a job and carries out the work properly as required, there is no harm on him in keeping that job or in benefiting of his certificate and the earnings from his job. Please, refer to fatwas 81709 and 87821.
Shaykh Ibn Baaz was once asked, "A man got a job because he holds a certain certificate but he cheated on the exam for that certificate. Now he is doing the job well, according to the testimony of his subordinates at work. What is the ruling on his salary – is it lawful or unlawful?" He replied, "There is no harm on him, Allah willing. He has to repent to Allah from cheating. If he is doing the job as required, then he bears no sin with regard to his earnings; however, he did wrong by cheating in the exams and he has to repent to Allah of that sin." [Majmoo‘ Fataawa Ibn Baaz, 31/19]
Allah knows best.