I have a itchy blister on my foot, the puss look yellow, I recently started using Nicorette, (nicotine gum) it's in he arc where my trainers don't rub?

Athlete's foot. Tinea pedis has various patterns and may affect one or both feet. It can have clusters of blisters or pustules on the sides of the feet or the instep. Try an over the counter antifungal cream to help with the itching and to clear it up.