Yes, those look like eggs that a fly has laid. The maggots are the larvae from the eggs.
I worked as a vet tech in another life and there was a cat who had an anal sac abscess. By the time it was realized that this cat had a problem (cat lived outside and the abscess had busted on its own) flies had 'blown' the wound. The wound was raw and full of eggs.
I can't tell the size of what is in your first picture that you posted but it could be the eggs from a fly, that would if hatched become the maggots. Seeing as how the maggots have sections and what you posted is smooth.
I don't know for sure about any of this, just throwing things out there for you.