It looks like Pokki has a superficial infection on the skin of her neck. If she frequently wears a collar, this area can be prone to infection if the collar is not kept clean and dry. Rarely, pets can be allergic to the nylon material but this is very uncommon. It's generally more related to the collar being dirty/oily or getting wet. Sometimes parasites can also cause this type of rash as well. At home you can try washing the area with an antibacterial hand soap and rinse well. You can then apply a dab of coconut oil to the reddened bumps. Rub it in well. If this does not help within a week, make an appointment with your vet. That being said, if you wish to go ahead and have her seen, the doctor will provide medications that will clear it up faster. I hope this is helpful. Please feel free to post any additional questions!