Here is my post to another backyard chickener... there is a couple of links you might follow to help with your decision making. Good luck!
OK, lets talk the difference between frostbite and favus! Frostbite looks like the area is dieing because the area has frozen. Favus begins with what appears to be white powder on combs and wattles and then begins to crust over in black. Mostly because the favus is eating into the flesh and causing it to bleed.
Here is a link of frostbite pics...
https://www.backyardchickens.com/forum/viewtopic.php?pid=3484665
Here is a link of favus (ours-which was diagnosed by a poultry vetrinarian)
https://www.backyardchickens.com/forum/viewtopic.php?pid=5437011#p5437011. Honestly, I posted when it first appeared and everyone said FROSTBITE! Now my entire flock has favus and I get to doctor 18 chickens everday for atleast 30 days.
If you even think it's favus begin treating promptly!!!!!!! If there is a pharmicist close by he can order bigger tubes of generic monostat cream with an active ingrediant of miconazole nitrate 2%.
Here is a link to a study I've found on treating favus...
http://www.ncbi.nlm.nih.gov/pubmed/8719227
Worst case, if you're not sure contact your local county extension officer and see if they can help or point you in the direction of someone local. That's what I did and it's paying off.