First off, great job buddy! That was one of the best threads I have read in some time. Keeping after it in the late season and enduring the cold like that with a buck on the ground is just top shelf
As for the worms, they are a part of the round worm cycle. It happens in alot of animals including humans. The worms are ingested in food/dirt etc, then migrate from the blood as eggs then moved to the lung/trachea. The worms go by several names (Gape worm, syngamiasis, gapes) but are just a parasite. I killed a mature whitetail buck several years back and his trachea/lung was loaded with them. He just needed to be wormed
I obliged him with a heavy arrow wormer much like you did!
Great shooting and congrats on the grey ghost of the mountains