Hi @dino_buenviaje1 
Welcome to the Canvas Community. You should be able to simply input a new score yourself for something either in the gradebook or through SpeedGrader. It will essentially "overwrite" your previous score. If it was an online quiz that was automatically graded, however, you will likely have to use fudge points depending on the types of questions involved. (Though that link also points to some additional material on a quiz regrade.)
If everything you do in Canvas is somehow tied into your student information system's grading system, you might have to contact someone locally about this, but that should be it.
Hope this helps a bit, Dino.
