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 proficiencies for heavy equipment, he'd probably lose those too, but I'd prefer to use a rule set rather than eye ball it.

The party is 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?