Looks like fruitworm damage.

From the FAQ section:

Tomato Fruitworms - are also referred to as the Corn Earworm. They are green, brown, or pink with light stripes along sides and on back; up to 1 and 3/4 inches long and are the larvae of various moths. The moths lay eggs near the stem of the green fruit and within 1 week the hatched larvae bores into the fruit where it feeds. It may move from fruit to fruit until it is ready to fall to the ground where it pupates till the following spring. Discard portions of fruit that have earworms in them. Disk or rototill plants immediately after harvest. Organic/Biological Control:
Parasitic Trichogramma sp. wasps parasitize tomato fruitworm eggs. Bt, (Bacillus thuringiensis) can be used for control of tomato fruitworm. Birds may feed on larvae. Moles and tilling destroy the pupae. Chemical Control:
Sevin 5% dust. Treat every 5-7 days when fruit begins to set as once inside the fruit the pesticide has little or no effect. Continue as long as fruit is present, if needed.

I found what sounds like the above on one of my green tomatoes happily munching a perfectly round hole in it yesterday. It was very small and was brown with stripes. I had never seen one like him before.

If there are any more of them, they will get a dose of BT along with my hornworms today.