Does Sweating Cause Pimples Around Opening Of Anus?

hi i am 18 years old guy 'Straight Guy', Its really embarrassing for me talk about this topic so it started off as diarrhea about 2 days ago and than i formed this pimple on my anus 'its right where is opening of my anus' it white like pinkish color it kind of looks like the pimple you get on face, its about pea size its very uncomfortable when i sit or drive car and i have recently been working out 'lifting weights' so my butt sweats but i am a very clean person i clean every part of my body so can you give me an idea what can be the cause of this thing i have lol thank you very much