Certified GKH Gardening Expert
Those green bumps are, likely, new root nodules that will form just about anywhere up and down the stem.
The reasons that your tomato plant is not growing could be many. Common issues that will cause slow growth include: Not enough sun, too much water, not enough water, poor soil fertility, low humidity, high temperatures, low temperatures, insect damage, fungal infections, and even much more.
Depending on how the plant looks, and whether it is in container or in ground, along with many other factors will determine the exact cause of slow growth.
For now, this article will help you with the care of tomato plants: https://www.gardeningknowhow.com/edible/vegetables/tomato/growing-tomatoes-guide.htm