saving a yeast starter

I made a 10 cup starter of American ale yeast 24 hours ago for I brew I was planning for tomorrow. Plans have changed and I can no longer brew as planned. I don't want to dump the yeast as that's a waste. If I want to save it, can I decant off the wort and save the yeast on the bottom of the starter in a sterilized mason jar? If not, is there something else I could do? I will be using it in a week or two. Thanks for any insight or help.

Yes, that will do just fine. Just fill up any headspace with sterile water.

if its only for a week or two, you should be ok to just leave it on the beer in the fridge. I usually bottle some of my yeast from the starter so that I have a culture for my next batch and its always just stored on the beer. I have not had any issues with this yet even when I keep the beer on it for a few months. Its a lot smaller than a full starter but I wouldn't be surprised if you are ok to just leave it.

Before putting it into the mason jar, should I cold crash it? By sterile, do u mean preboilded water or distilled water? Also, would u do another yeast starter to get it going again?

for a few weeks i wouldn't decant the beer, but i would get it into a sanitized smaller vessel with little air space and a sealable cap (don't tighten it all the way though, you will probably have a bit of residual activity or at the least CO2 still coming out). i like to save yeast for re-pitch, or starters that are waiting for their wort, in 1 liter screw cap jars that can be easily sanitized, filled to the top with the beer they were living in, or else topped up with boiled and cooled water as necessary. after a couple weeks storage, i would not make a new starter, i would be happy to pitch that yeast, but you can always feed it a bit of wort a few hours before pitching to get it active. to do that, i decant it while it's cold (since some yeasts will go straight for the surface as they warm up), let the yeast cake warm to room temp, then add similar temperature wort; while i am cooling my wort i run some off and cool it quickly in a water bath.