I almost answered yesterday, since no one else has I'll venture a guess. When I was a kid we had a volunteer peach tree, so I know that it can be done. In general seeds contain every thing they need to sustain growth through a certain stage. Usually no fert is needed until after true leaves start to come in. I'd recommend some espoma biotone starter.

What type of mix did you use to start it in?

Many nurseries start trees from a branch to get earlier fruit and true to variety. If you are sure that the pit you used was heirloom it shouldn't be a problem, just something to think about.

I would not fertilize until the first true leaves are well developed. Until that time the plant is growing off of seed nutrients and root development could be affected by the fertilizer.

Your pear is almost certainly from a clone spliced onto a different root stock, and pear trees produce more fruit when fertilized by pollen from a different clone, so your seed is most likely a hybrid that will not produce fruit like what it came out of. But it is still a pear and I never met a pear I didn't like...except those nasty tasteless green anjous from the supermarket.