I will let the experts pop in and give you an opinion but if it were my plant, I wouldn't be all that concerned by that small amount of whatever it is. Truthfully having plants just go through normal everyday living stress they get little blemishes...I'd say it could have been as simple as a sun scald maybe there was water ...or I've created that sort of thing from sprinkling fertilizer on my plants.

Does it look like the photo in the link below? From the U of WI: "Blossom end rot is a disorder associated with the temporary shortage of available calcium in the fruit. It is aggravated by soil moisture fluctuations. If water is limiting, plant growth slows and subsequently, nutrient uptake is reduced. This reduces calcium concentrations in the plant since calcium is carried through the plant in the water flow. Because calcium is carried along in the water stream, those plant parts that are transpiring most rapidly will receive the most calcium. This is often the oldest leaves since they are the largest. Developing fruit is least likely to receive the calcium it needs. Moisture stress that results in even partial wilting of the crop is enough to cause a calcium deficiency. Once moisture is available, the plant resumes regular growth but calcium uptake continues to lag and the rapidly-expanding plant doesnÂt have enough calcium to develop properly. Applying nitrogen as ammonium also appears to directly affect calcium uptake by tomato plants. This produces a reduction in calcium absorption and accumulation in the tomato leaf tissue. The incidence of blossom end rot is reduced by providing even moisture and avoiding excessive nitrogen fertilizer applications. Although varieties do differ in susceptibility, there are currently none with sufficient tolerance to provide dependable control. Timely and repeated spraying of tomato fruit and foliage with a dilute solution of calcium chloride has been reported to prevent blossom end rot but the benefits are often variable." Sue Here is a link that might be useful: Photo: blossom end rot in a tomato

The white stuff are whiteflies and their eggs, we have an infestation problem with them in South Florida. Whiteflies are from the tropics and can carry a disease called tomato yellow leaf curl virus. Leafhoppers also carries it. Once your plant is infected with leaf curl virus, the plant will almost stop growing and not produce anything, there is no cure. I'm not saying whiteflies definitely carry the virus, they may not, but it is something I've very wary of. I was not able to grow tomatoes for the most of 2015 because of them. Whiteflies like warm temperature so there are much less of them during the cooler months. They prefer shade, warmth, and protection from wind. They are attracted to nightshade plants, the virus infect nightshade plants such as tomato, pepper, goji, potato, basil. But they are attracted to a wider variety of plants while not infecting them, like the "bidens" plants (common lawn "weed"), brassica crops, banana and other type of leaves that may provide good shades. This season growing tomatoes in spring with the cooler temperature I have less problem with them. Also with mulching and keeping the plants healthy reduces my pests issues. I notice whiteflies like to attack the lower sick leaves, so I pruned them and maintain a good airflow in the bottom.

Bumps are likely edema, which is a condition brought on by high humidity or overwatering. Frequently see those bumps on the stem as well. Not a big deal, though bad edema, with bumps all over the leaves, causes leaf loss. I'd just ignore it.