The ‘lump’ is actually not a lump at all but a counter-reaction to the body’s automatic nervous system. When humans are exposed to stressful situations, the body automatically increases blood flow to vital organs and muscles. This is our typical ‘fight or flight’ biological reaction to things. Consequently, in order to get more oxygen to the body, one biological response is to expand the glottis in your throat.
But, being the social creatures we are, there are times when we try to suppress the urge to cry and often constrict or stop breathing altogether. Hence we have a battle between the body’s natural response to stress by widening the muscle in the throat to get more oxygen, and one’s wish to avoid shedding tears where we often stop breathing and thus constrict the muscle in our throat. Hence, the vocal chords are fighting themselves to both compress and expand at the same time - and that's when we experience the tension as a lump.
But, being the social creatures we are, there are times when we try to suppress the urge to cry and often constrict or stop breathing altogether. Hence we have a battle between the body’s natural response to stress by widening the muscle in the throat to get more oxygen, and one’s wish to avoid shedding tears where we often stop breathing and thus constrict the muscle in our throat. Hence, the vocal chords are fighting themselves to both compress and expand at the same time - and that's when we experience the tension as a lump.