Help, my canary's neck is black!

Hi, my name is Pedro and I have a male canary since August and, yesterday, I've noticed that my canary's neck is black and it looks like blood and it's missing some feathers ...
He stopped singing and he looks pretty sad, I don't know if he is dying...
One day (before his neck turning black) he got stuck in his food place and I needed to take him out of there, but he didn't look like he was hurt...
Please, help me.... I don't know if he is molting. View attachment 284572