Hi,

You can change this during the UGC NET Correction Period for 2021 exams. The dates for corrections were 12th March to 16th March. However, in any case, if you missed the deadline and forgot to update the income, there shouldn't be much issue.

In general there shall not be any problem with the income status except if you have applied for EWS Quota because it depends on someone’s income and misfiguring data can lead to cancellation of seat through that reservation. Since, you are from SC category, it shouldn't bother you.