Hi Aspirant,

OMR sheet is a sheet which is recognizable by the computer.So in case if you have smudged a ink you could have discussed the matter with the invigilator.It could have been some help.As in my case it once happened that the invigilator offered me some whitener to remove the stain in one of my mock test.However if the roll number is understandable by human eye then you are on the safe side.

Hope for the best!!