S/o discipline, biting at 9mos?

historychick79

DS loves snuggling into my left shoulder, and has recently decided it is 'fun' to take a small chomp while he's at it. Twice he's left marks. So far, I've given a stern 'no bite, ow' the first time or two, and if he goes for a third time I repeat and put him down and wait about 10 secs to pick him up; this usually results in him howling and me feeling like the meanest mom ever. I know you can't really discipline at this age, but is this appropriate; do you have any other tips?