First Tomato Flower Bud About To Open!

I didn't even know this plant had a bud set yet. I was checking on them last night & saw a good sized (about 1 and 1/2 cm) bud on one of my tomato plants that looks like it's about to open! =) I'm excited, but this means I need to get them outside in the cold frame soon, or the flowers may drop off the plants. Here's a pic of the bud. The color in it is miserable cuz it was taken at night with my camera phone.