It seems unlikely your plastic spoon would have scratched your bucket, though it is possible. The way many folks scratch their fermenters is during the cleaning process. Avoid using the abrasive side of your sponge. You can clean it effectively with a long soak in PBW or oxyclean. Then a soft sponge will typically do the rest.
Now that you do have scratches, you need to be very careful about sanitation. Scratches are great places for bacteria to hide. The best way, in my opinion, to sanitize your container is to fill it completely with a no-rinse sanitizing solution, and let it soak for a long time. Typically I will fill it after mashing in, then drain it as I approach the end of the boil. By the time the wort has cooled sufficient to transfer, the bucket will have air dried.
I've been using the same bucket now for nearly 15 years without a problem.