what happens if i get approved for disiability after i file for chaptor seven

No, it will not.  Insofar as the means test is concerned, for Chapter 7 “current monthly income" you don't include Social Security retirement and disability payments.  Additionally, as far as creditors are concerned, these are exempt funds and thereby are not considered assets of the probate estate. You still may, however, want to disclose to your bankruptcy trustee the fact that your are receiving them (if you are in fact approved to receive them).