Couple things you can do. First, spray foam will probably melt the surrounding foam before it hardens. I use it for filling voids in balsa or fiberglass areas, but not foam. A test on some other foam would tell you if it would work. It would be the easiest way to fix it. You can also cut out an area of foam and glue in more with Gorilla glue. Shave off flush and go from there, or, use light weight filler to fill the hole if it is not too deep. This will take 24hrs to dry, but it will sand nice when it does.