you can run tube down his throat see if something stuck in there. Look down his mouth with flashlight see if you see something. Give him some tylan in case of cold in gland or infection. Give him hot pack on neck see if that helps. Take moist town and put in glad baggy warm and put up next to neck. All things I would do. I would even run tube from his mouth to crop and fill him up with food if he is weak I like to give them ensure plus. If nothing stuck in throat give him penicillin shot and check for mites. I might give him 0.06 ivenmectim under skin on back for worms (dose depends on size, that what i give full grown chicken). If no ivemectim then I would at least powder him for mites. Hopefully all that helps. Is hard to give advice when cannot see him.