I forgot to add nutrient to my must when I put it in my carboy the other day (first time brewing mead). I fear I won't be able to get to my homebrew store before it's too late, so I'm wondering if I can create nutrient at home. Is this possible?
you can boil half a sachet of yeast and add that to the must. It provides many of the trace elements needed by the yeast, but I'm not sure how much nitrogen it provides, which is the key nutrient required in mead.
If the mead is not very strong, you can in fact successfully ferment without nutrient, just pitch 50% extra yeast.
Also keep in mind that mead long predates yeast nutrients. The old Greek formula went something like:
That must have been some sweet, syrupy mead. However, the point is that if you can't get the yeast nutrients, you can always try brewing mead without them.
FWIW I have always brewed a very rustic mead--- no degassing, no yeast nutrients, just yeast, honey, water, (4:1 btw, so drier than the early Greek varieties), and optionally some additional things to flavor it. This has always worked well for me. I have been brewing mead now for about 20 years and never found the need to do this. So keep in mind that you are brewing an old beverage which was simpler in times gone by, and so failures of process are very gracefully handled. My advice is don't sweat it too much.