Weird pimple on my left breast? :(

Ok so, I just want to make it known that I have never been pregnant, never lactated, and I’m only 20 at the time of posting this. Today I noticed there was a pimple on the underside of my left breast, and it’s not like the other occasional pimples I get whenever I’m close to my period (which are rather soft and small, and go away in a few days). This bump/pimple is hard, and if I try to touch it, it just feels numb. I tried to squeeze it a little and scratch it a bit to see if it would hurt, and nothing. It more so feels like when your foot falls asleep and you scratch it; that kind of weird sensation. Does anybody know what this could be? I’m really hoping it’s nothing serious; I’m really worried that it may be something bad :(