So I've managed to round off my inspection cover bolt so it won't come off. (not my fault it was bad when i got it)

I guess it's no biggie as i can just take off the whole cover, but I was wondering for the sake of neatness, could I filler around the bolt to just smooth it over? (I need to paint it anyway) Would the heat be a problem for standard automotive filler?

Cheers chaps,
Nielsy