It means that he isn't going to worry about itThe whole quote goes like this:"And also with the result of causing it to turn upon its masterat the other side. Some of the blows of my cane came home, androused its snakish temper, so that it flew upon the first person itsaw. In this way I am no doubt indirectly responsible for Dr.Grimesby Roylott's death, and I cannot say that it is likely toweigh very heavily upon my conscience."