Hi My Son Has Ringworm Which Has Become Infected. The

Hi my son has ringworm which has become infected.
The area is raised and lumpy, painful to touch and has pus in areas.
Flucloxacillin Capsule has been recommended.
My son cannot swallow capsules so the doctor advised to split the tablet open and mix with yoghurt.

Is
a) the medicine going to be sufficient in clearing this, and reducing the swelling and
b) is administering it in this way okay? (with the yoghurt)

Many Thanks, Shantel