Tough one! Since it is at the bottom, and if you are not sure if the colour will be perfectly matched, you could have a good spray painter 'blend' the paint with the rest of the bumper. Enquire about 'blending' this piece and you don't have to re-spray the entire bumper.
However, if you are not pleased with the result, you could then re-spray the entire bumper.
I have heard of 'airbrush' jobs done on small repairs like this well. It's probably much more cost and labour effective to try to do the small area first.
Good luck! :thumbs: