It can’t go ‘inside’. It’s sealed round the back. Look (with your eyes, not your head) as far in the other direction to where the fly is and hopefully it’ll be visible. You won’t be able to see it though as you’ll by now be looking in the other direction. You need someone trustworthy who can then lift it out. in the olden days, the best qualified person would be your mum, ideally with an old tissue she’d found in her handbag twisted into a point. Nowadays, you’ll need a qualified eye surgeon obviously.
(If your mum happens to be a qualified eye surgeon, you’re well in clearly)
Your might try flushing it under running water as well – maybe even before phoning your mum.