L.L.
It does take some time. The dr did prescribe cream for mine when they had it and Nizoral shampoo (at Walgreens, cvs, etc) is awesome go wash every day before applying at bedtime. Just be patient and consistent--most importantly!
Keep it clean and dry before applying and it will go away. Keep his nails trimmed just in case he scratches while you are not looking, because it the ringworm can spread.