Personally I’d leave it alone until it gets worse or something happens that requires paint and body and address it then. I wouldn’t notice that on something that’s driven and used.
But if you gotta...
That’s metal, isn’t it? Is it easy to remove? Id try a home repair using the correct auto paint in a rattle can. You’d run the risk of it not being a perfect match, but since it’s a bumper and not a body panel I don’t think you’d notice or that it’d detract any. The only downside is it’s a little tricky, for me at least, to lay down an even coat of clear using a rattle can. Bright sunlight helps.
I’ve been meaning to share this a while now. We all know our phones spy on us and send us targeted ads. I’ve been getting this one ever since you cobbled together the cardboard smoker and made biltong. I’d never heard of it before and didn’t mention it to anyone but apparently my phone knew I was intrigued.