are there any other roosters in the flock? Are you seeing any changes in the combs of your hens... so this is what I am thinking could be from fighting/pecking, due to frost although that grass looks nice and green, or could be fungal which would require antifungal ointment... that's what comes to mind when I see this.
This could be caused by rubbing his head on something will roosting. How crowded is your roost boards? Are they too close to the top of the coop/pen? Is he rubbing his comb on wire or some other rough surface? My guess would be trauma from the other birds or trauma from hitting his comb on wire/wood when roosting. I rarely see my birds fight but I do see the result of it.
That happened to all of my chickens when we got a buff orpington and placed her with my others they all started pecking each others combs, my hens combs started bleeding and when the blood dried that is what it looked like, it healed in a week or two. maybe he got into a fight with a hawk or something else.