Those are seeds developing, but you need a better picture to find the male banana parts responsible
Did you have a male plant in there? do you have femmed seeds?
If you did not knowingly have a male, then a hermie, whether this plant or another has released some pollen. Take a careful look at all your plants. Your the proud parent of some seeds.
Which should binned! No one should be growing out hermie seeds unless they want more hermies. Over argued subject here, do some reading on the subject.