I know that the received wisdom is this business of the roots being cramped, but with hardy varieties, I've found they do perfectly well in open ground without root restriction. In fact, I did what you've done, kept mine in a pot wondering why I had so few flowers, and after seeing three huge clumps smothered in flower in a friends garden, I stuck mine in the ground, the following year it had several flowers and never looked back. doesn't work for varieties that need shelter over winter, so its up to you whether you pot on or plant out. Don't split, just repot, they're not bulbs, with only two flowers, doesn't sound like your plant is yet big enough to split.

thanks!