I am on a student visa (F1) and currently on Optional Practical Training (OPT) and am staying on status legally. My sister, who is a US citizen, has filed I-130 for a green card. In the meantime, I've thought to go back to my country and come back for a graduate school. Will it be problematic while entering the US? Coz I have pending I-130 case and am on student visa. Please suggest me, what I could do
It may well be problematic, since the F-1 requires nonimmigrant intent (the intent to be here only temporarily for the purposes of your studies, and then to return home abroad). Having an I-130 on file demonstrates intent to emigrate here permanently.
The category in which your sister filed has a very long wait for visa approval - over ten years if not more, at least going by the current Visa Bulletin. It may be possible to convince immigration you are aware of the long processing time and are seeking further education only to make yourself more marketable in your home country while you wait.
Speak to a lawyer concerning how best to document this, if you choose to proceed.