PlantLife Online

Answer

It appears to be a case of Blossom-end Rot (photo of the bottom) which is a physiologic disorder associated with a low concentration of calcium in the tomato. Calcium is required in relatively large concentrations during the fruits development. A lack of calcium during development will cause the tissue to break down, leaving a dry, sunken lesion at the blossom end. The nursery which told you to add Bonemeal was good advice, bonemeal is a good source of organic calcium and phosphorus mostly with some other nutrients in small amounts. Generally bonemeal is a slow release fertilizer however the finer ground the bonemeal the quicker it is available to the plants in your garden. It could be that the bonemeal you used was a course ground or excess water leached or washed the nutrients away. I would recommend using bonemeal again next year along with an organic tomato specific fertilizer to cover all your basis. Be sure to work the bonemeal and fertilizer into the garden soil.

The cracking in the top photo known as "Growth Cracks" is a symptom of extreme wet conditions followed by drought conditions during the tomatoes development. This can be avoided by creating a consistent watering schedule for the garden, don't allow the soil to completely dry out between waterings.