It looks like it could be either a peck wound, a sting, or possibly a respiratory such as MG or coryza. It may respond to an antibiotic such as Tylan or oxytetraxycline
If it was caused by a respiratory disease, then yes, this bird is contagious. But, the spread to any other exposed birds has already occurred. Can you tell us a bit about your flock history, and any other symptoms he has? A clearer photo closer to his head would also help if you can get one.
it happened last year too but it was pussing + she sneezed a lot. But this year it doesn't seem to bother her much. Allergies? Rest of my flock is fine
Unfortunately, chickens don't really get allergies or a cold. They get respiratory diseases. It does sound like she might have respiratory illness, especially if she was sneezing often. It could also be an abscess. Have you ever had any of your other chickens sneeze or gurgle or have any other problems in the last year or so?
Most respiratory diseases are chronic, make carriers of the flock, and can come back whenever the chickens are stressed. Injectable Tylan 50 may help if given at 1 ml daily for 3-5 days. Here is a good link about the most common respiratory diseases and symptoms:
Sorry that I didn't post the link for respiratory diseases, but here it is now: http://edis.ifas.ufl.edu/ps044
