Wa`alaykum as-salam wa rahmatullahi wa barakatuh.

 

You have committed a grave offense by cheating in the exam. You ought to repent and seek forgiveness of Allah.

Your income becomes pure and lawful only if you take immediate steps to rectify the situation by honestly studying the subjects you cheated and ensuring you excel in them. Since a mediocre doctor can endanger the lives of his patients, it is not permissible to practice medicine unless you are suitably qualified.

Therefore, you should change the field if you lack the confidence to succeed.

You also need to offer charities and make lots of istighfar to expiate for your grave sin.

I would also remind you repentance is acceptable only – if one fulfills certain conditions, which include the following:

1. Refraining from such sins in future
2. Feeling remorse over one’s sins;
3. Resolving never to do the same;

Finally, one ought to compensate for such sins through good deeds; Allah says, “Good deeds wipe out bad deeds.” (Hud 11:114)