How much will nurturing a hatchling affect its aging process?

Nurturing a hatchling boosts its stats rather than its age. The weakest stat is the one that is boosted by nurtures and 5 nurtures boosts the stat by 1. However, hatchlings can gain a little maturity as each profile view increases its maturity by 1 (216 is the adolescent maturity and 648 is adult, to give you a baseline). It has to be a profile view so the nurturing must be from the actual profile page itself.

Hope this helps!