A tiefling sorcerer wild magicked himself from 22 ish to about 14 biological years old. Physical change only.

While in this state, I'd imagine his strength and Constitution should be lower and if he had any proficiency for heavy equipment, he'd probably loose those too, but I'd prefer to use a rule set rather then eye ball it.

The party are pretty far from any civilization, so he could be in this state for a while.

Are there rules for adjusting ability scores for this, official or otherwise?