Hello As you mentioned that sometimes a knot develop on anal opening ( in your anus according to you ) , this may be hemorrhoid and still it is very small in size . So take nifedipine ointment ( or any lignocaine type ointment for local application on this lump or knot). One thing I want to tell you in what ever condition , don t go for defecation until and unless you don t feel a full pressure ( urge for defecation ) . Whenever you feel that now , you can t control stool then use toilet , otherwise wait for it . Take high fiber diet for constipation if any . Plenty of fluid also help. Still no relief then consult a physician and get his opinion. Good luck.