Hello there, an interesting question here. Nail pitting is an extra-articular manifestation of psoriatic arthritis. In children, 30% of children with psoriatic arthritis may have nail changes. In adults, the prevalence is 50-80%. There are other extra-articular manifestations of psoriatic arthritis.
Treating psoriasis & psoriatic arthritis mostly should treat the nail changes too.
Next Steps
There is a need to meet a Rheumatologist