Throw a couple pictures up.
In theory you would sand the run then mist another coat but rattle can enamel doesn’t sand well for a few days by then the stencil could possibly bond.
Water sanding would be best for a fragile finish right now because it is more forgiving but water sanding wood is likely to make it swell or grain.
Anyway put a picture up of the issue and what you sprayed it would help better advise.

Sometimes you just have to start over.

Don’t worry about it. Happens to any painter despite their experience sometimes.
When I was a painters helper long ago the old timer I was working under told me this after I f’ed something up despite putting a lot of time and effort into it.
“Paint is like a relationship with a woman. Sometimes you can do everything right and it still goes wrong” (2021 disclaimer women feel free to reverse the analogy)

You have a bit of a disaster there honestly.
Even if you fix the yellow you might find that when you pull the stencil up you pull the black up or have a bunch of glue left behind.
My best advice knowing how long the stencils have been on there and seeing the picture is to order another stencil set.
Once it arrives
Pull what you have on there up.

Sand the messed up side flat including the bondo.
Black that side out again and do it over.
If the the other side ,front and head look fine you are back to a workable position and only have one side to redo if not you have what you need on hand to continue on starting over in full.

I am not saying what you have there couldn’t be salvaged. I could definitely do that myself but with your admitted lack of experience you are probably going to end up deeper in the weeds than you would just biting the bullet and starting over.
To avoid runs just spray the cabinet one side at a time laying flat on its side instead of in the natural position.