If it is just a couple drops of oil it may or may not need a bleed. The grittyness likely has nothing to do with the bleed and was most likely there the entire time. You can tell if it needs to be bled again by how much braking power you have why applying the brake and how far the lever throws. If the brake is lacking stopping power bleed it, if the lever pulls all the way to the grip to get power bleed it, if it has the same power and throw as before (grityness aside) its fine you can leave it be.