Hi and welcome to the forum! I am glad that I can help you.
You want to know the cause of the symptoms that you experience.
Bumps in the neck may appear due to muscle strain or tear, inflammation of the lymph glands, inflammation of the skin, or in rare cases inflammation of the lymph nodes and skin due to tuberculosis. In cases of muscle strain individuals experience pain during limb movement or in cases of a tear they experience difficulties moving a limb. In cases of inflammation of the lymph nodes or skin, the skin is painful, red, swollen and hard.
According to the data that you describe, you may or may not experience any of the medical conditions listed above. See your doctor for further diagnosis to rule out muscle strain or tear, inflamed lymph nodes or skin.
Please keep in mind that I provide medical information only. I am not able to diagnose medical conditions online. Please contact your doctor for further advice and information about diagnosis and treatment options.