What should I do after completing B.Sc (biotechnology)?

If you want a good job then go for Master's degree. At Masters level, you will have better idea of what to do in your field.

Pursue Masters and add to your research skills. You shall have job options with government research platforms and Master degree will also lead you to UGC -CSIR test that will make you eligible for higher education teaching jobs. However, research remains an appreciative option.