Possibly a peck wound at the top of the eye. Looks like the eye may have been pecked too?
Eye looks like it is infected and has a discharge either from being pecked or possible respiratory infection.
Wash the eye with saline and clean out any pus. Apply some vetericyn eye gel or terramycin eye ointment.
I understand you are not with your chickens at the moment, but if you can get some clearer photos that may help.
As @sourland asks -- any other symptoms--coughing, sneezing, runny nose - any others in the flock showing any symptoms?
May want to separate this one just in case it is respiratory infection and not infected from a pecking wound.