Greetings, sorry about your concern.
Just understand the basic development of a kid, Until your kids 13 th year bones solidification happens, meaning they develop into a full functional bone.. So until then they cannot fully bear weight of the body. This is normal for any kid.
Having said that if your kid frequently falls or if he is not able to stand straight and has a tendency to lean on one side, then this a postural deviation. Since foot is the first structure which comes into contact with ground and if muscles are not supporting them, foot turns inwards.
This can be corrected by a physiotherapist specialised in postural correction.
Next Steps
normally exercise for hip and foot plus braces ate used to correct this. physio will guide you. in 4 to 6 months your kid will be back to using his foot normally
Health Tips
not to be worried, this can be corrected. if for reasons you cannot find a physio or find solutions just bring your kid to me will do the needful.