Rejected Return

My return came back as Rejected after I E-Filed.  I had filed as Head of Household since a nephew lives with me and was a Student last year and only made $207.00 last year and was fully supported me.  He filed his taxes in April in hopes of getting a stimulus check which has not happened.  From what I can see is that I need to change his filing status  in order for me to claim him as head of household.  How do I do that, I am freaking out about this last year I worked part time plus I collect a pension and Social Security this year because of the pandemic I have barely worked since I am in a high risk category and the work that I do has decreased by 80%.