I am having a lot of pain in anus while doing potty, I am sure it isn't a constipation

Hi I am 25 years old and I am having a lot of pain in anus while doing potty .its not constipation because I am in regular note and it's not hard for me but whenever I go for potty it burns and pains a lot as if something is stopping from coming out of my Anus and I can also feel some bump , not exactly bump but something unusual in my anus when I tried to touch it with fingers and I could not see that as it's not visible and deep inside . But it gives me hell pain whenever I sh*t . I want to know what is it and what's the solution