ORIGINAL: Lubricious
Warble fly or bot fly
The warble flies, also called heel flies, or bomb flies, parasitize cattle and other animals. The larvae, called cattle grubs or cattle maggots, penetrate the skin of the host immediately after hatching; they migrate through the flesh, causing irritability, loss of weight, and decreased milk production, and then settle under the skin of the back, producing cysts, or warbles. Breathing holes made in the warbles by the larvae damage the hide.
How sure are you? Is this a common thing? I've never seen this before, i've butchered a ton of deer, thats why it has my attention as much as it does! Is there anything else it could be? And if what you said is right, can it be eaten?