Since you did not declare at entry, you will likely be refused. The rules do not change just because you are inside the US. You are indeed a poor candidate for a visa with your sister on a GC likely when she was also previously a student. Go home and reapply properly. Quit trying to scam US immigration officials by trying to run around the rules. If you do not qualify, study in your own country and come on an guest worker visa in the future which has different rules about returning to your home country.