If you want it fixed permanently the right way, here's what I'd recommend...
1) Scrub the area with SEM Scuff & Clean # 38338.
2) Wash the area down with water and dry it off.
3) Mask off the damage.
4) Spray the damaged area with SEM flexible bumper sealer # 39113.
5) * Fill the damaged area with SEM flexible polyester glaze # 39482.
6) If the plastic is textured, then transfer the same texture to the glaze.
7) Carefully finish sand the area.
8) Paint to match.
* If the scratch is deep enough (it doesn't look too deep fom the pics), then fill the deeper parts with SEM problem plastic repair material # 39767. This stuff is compatible with 90% of the plastic bumpers used today including polyproplyene, EPDM, TPO and similar substrates. If your bumper is made from urethane, or PUR, or RIM, or TPUR, then you'd use #39927 instead of 39767.
Or you could use bondo and hope for the best or live with it or take it to someone who does this kind of work.