I'm an F-1 student, filed my taxes electronically. what the problem is that I filled out the 1040 form instead of 1040NR. Also I came to know about this after I got my refund. Will this affect me in the future because I must apply for a H-1B visa next year.

so what would be the next immediate step for me to do???

For 5-years on F1 you are exempt. You must file nonresident tax return. It can't be e-file; must be paper return.
Now you will do your nonresident return, amended tax return Form 1040X and Form 8843 and send to IRS. You will get deduction as per tax treaty between your country and the U.S.

I have combined your two posts, please do not start a new question *thread * to merely ask for additional info, please merely reply with an answer to your own question, with followup or more info

If you ask a new question ( thread) it will no be linked so no one will have any idea what you are talking about.

MyDear:

You also have the problem that you may get the stimulus rebate check, a check to which you are NOT ENTITLED.

Do NOT spend that check. You will need to return it when you amend your return by filing Form 1040X and attaching a properly-prepared Form 1040NR-EZ.