according to one article on the web this is caused by a split stem. "

Split Tomato Stem

Tomato
stalks are brittle vines and split easily in strong winds, under the
weight of a heavy crop or when brushed against, hence the custom of
supporting and protecting plants with stakes and wire cages. In
addition, the stalkäó»s tough outer surface, or epidermis, is made
thicker by hairy bumps, adventitious roots that sprout near soil or
during periods of drought or high humidity. If plants receive a sudden
downpour after a long dry spell, the xylem, which carries water to the
plant, swells, occasionally bursting the epidermis in vertical cracks.
Sudden extremities in moisture and temperature can cause cracks in
stalks, as well as fruits.

If you have examined the stem (without doing further damage) to
eliminate a pest as the cause of this split stem, then you should just
allow it to callus (heal) over and the stem should function normally to
carry water & nutrients from the roots upward. Its not necessary to
tape the stem, in fact it could cause moisture to accumulate inside the
split area and possibly create fungal issues. If you have support
higher up on the stem, it should be fine."

The bumps are primordia, which are the beginnings of adventitious roots. They can happen when conditions are humid or you overwater your plants, or they happen a lot when damage or disease hurts the plant's roots or the vascular system of the plant. I would be concerned about disease, given the color of the stem areas in the picture. Is your plant wilting or yellowing?

Have you sprayed an herbicide any where in the vicinity. Damage could be from drift of 2,4-D or something similar.