When you say popped do you mean that it broke open and oozed gunk? If so, I wouldn't treat it as if it were a wart. Warts don't pop.
If you mean it showed up about a month ago it may be a wart. My plantar warts are not raised above the surface of the skin and so I suggest that it is not a plantar wart.
Warts are caused by a virus and are easily spread. The safest thing to do is to take him to the doctor or if the clinic has a nurse treatment office to it..
Or, an old fashion way of treating warts is to cover them with duct tape for several days. I have not used this method but have read in many places for many years that it is effective in removing warts.
I have tried OTC treatments and they have never worked. I've had many warts and had them removed at the doctor's office by freezing. They aim a very cold steam like stream from an aerosol can.