It looks like there could be an eye infection from an injury or a possible respiratory infection. The third eyelid or nictitating membrane looks inflamed and swollen, and there is crusted eye drainage and possibly nasal drainage. I can't even see the eye there; can you see it? Is there any other symptoms of a respiratory disease? I would definitely take the chicken to a vet, since it may need some good antibiotics.
Vetericyn gel is good in the eye, but he needs some antibiotics. If it is a respiratory infection Tylan 50 injectable given as a shot or given by mouth would help. But if it is an eye injury and infection, he could lose his eyesight without something stronger. Baytril is banned in chickens, but it still is given in pet chickens by some vets. There are other medicines too available.