YES, Lowe's sells a wood filler by bondo. Mix it and shape it in, a little bigger than you need, then use a palm sander to make it even with the sides after it cures. Once painted it looks great!
I did this on a Frogger cab that someone dropped and broke a 3 inch section off the top corner. Molded it to the right shape and sanded and painted. Used a sutting wheel to make a grrove for t-molding. After it was painted you couldn't tell it wasn't original.