Red spot on baby arm

It’s hard to tell from a photo alone, but it looks a bit like eczema, a fungal rash (ringworm), or a skin irritation/contact dermatitis. Since you mentioned it hasn’t improved and has been there since starting infant care, it would be a good idea to have a pediatrician examine it, especially if it’s spreading, itchy, or becoming more red. In the meantime, keep the area clean and dry, avoid new soaps or lotions, and moisturize with a gentle, fragrance-free cream if the skin seems dry. If anyone else at home or childcare has a similar rash, mention that to the doctor as well. Hope your little one feels better soon!