It is very difficult to see anything from that pic. I did blow it up and I am not seeing anything that resembles fowl pox unless the darkness of the pic is hiding it. So you might want to take a better pic in good lighting. It is possible the bird has/had frost bite. One of the tips of the comb looks a bit black. If the tips of the comb and edges of the wattles are black or even white as well, this may be frost bite. I would put some vaseline or even bag balm on the areas to help soothe and protect these areas from further damage and or pain. If you are having frost bite issues in your coop, you need get out the saw and cut holes in the eaves or ceiling of your coop to allow the moisture from all the pooping and breathing out so it does not fall back down on the birds as water or frost, causing this frost bite.
drumstick diva X2. It looks like another chicken was pecking at it or somehow scratched herself like drumstick said. I clicked on the picture and it brought it up closer to see. but there is no redness and it looks like a scar to me.