What Causes Painful Bumps After A Blister Burst?

i had 2 pimples on my arm that hurt i then poped them and they they hurt-ed a little more. me and my friends were playing a game and my friend squeezed my arm where that pimples are and now there is a lump on my arm and if i barley touch it it hurt ans it hurts when i stretch my fingers. what is that?