wombat
No, Don't throw it out! Either find something to weight the veggies down or use your (clean) fingers or an implement to submerge them daily. Also, do NOT seal the lids on the jars. Just set them on top, or cover with cheesecloth or something to keep dust/flies out. The fermentation process causes air bubbles, which caused your kimchi to overflow. The same thing happened to me my first batch! & it turned out GREAT!!! :D
If your jars are too full, drain a little of the brine. You need airspace in the top...