I believe he may have had an abscess in or around his ear. I would keep cleaning it very well and applying an antibiotic ointment (Neosporin, no -caine ingredients) to the area. I don't know that I would use systemic antibiotics unless the chicken was obviously more ill than he sounds. Chickens' bodies tend to encapsulate infections thus the reason for the weird pus. Infections are rarely oozy instead the infection tends to get hardened and isolated into a pocket (abscess), which is generally easy for the body to deal with long term and can be cleaned up pretty easily once the pocket is opened. Systemic infections from wounds are fairly rare considering how often chickens scratch and bite and wound each other. I think he should heal up just fine as long as the infection doesn't move into the ear or sinuses. If he should start displaying any swelling in his face or head or any balance problems I would start him on a systemic antibiotic ASAP.
Good luck with him. Keep us posted on his condition.
