Looks like your hen is infected with fowl pox. There is no treatment for fowl pox, but to prevent secondary infection (which is more severe than the disease), treat the bird with an antibiotic, such as Terramycin,. The Terramycin (also known as Oxytetracycline) dosage is 1/8 teaspoon powdered Terramycin per cup of drinking water for 7-14 days. During this time, do not give dairy products, such as yogurt, or probiotics. Vitamins/electrolytes are fine, though.
The fowl pox itself will run its course in a few weeks. Be aware that, though your bird has the dry pox form (the form that causes lumps outside of the body), it could develop the wet form, which is more severe. In fowl pox's wet form, sores/lumps infest the respiratory tract and throat. If they become large enough, the bird dies from suffocation.
Good luck with your hen!
