Or... rather, could the cold snap we just had here in PGH have choked the life out of the flower bud? It's been 'half open' for about a week now, with no change. Should I nip it and let the plant concentrate on other more productive things?
What's the variety name? If it's one with HT form and a lot of petals, it might never open fully. If's it's really bugging you, remove it.