I tried a search for this but got a bathousand results.
I love my Nickel Gen Bb but I find it takes a lot of air, so I experimented with flattening the windway a little (biting it) and it takes less air but the sound isn’t the same. 
I’m sad.
Is there anyway I can ‘open it back up’, so to speak, without risking making it worse?
How about trying to spread it open with a file or something?
Unless the plastic is too mangled.
I am probably not helping…
I’ve thought about trying scissors or something in it to open it up some more, but I’m skerred that I’ll damage it more.
It’s ok as it is, just doesn’t sound the same. After I bit it, it sounds ‘thinner’ and the upper end isn’t as easy.
Sigh.
I would recommend that you take a piece of credit card-type plastic or something similar, cut to width so you can fit it into the windway. Cut a piece of sandpaper that will fit into the windway also. Use the piece of plastic to push the sandpaper in the windway and sand off any variation in the windway ceiling or floor that was created by biting it. It works best if you have double sided sticky tape to stick the sandpaper to the strip.
After you’ve restored the windway to it’s original uniform flat surfaces, I would then laminate something to the floor, ceiling or both, depending on how high up in relation to the windway floor the windcutter blade edge is. It needs to be just above the windway floor, so you can see a little daylight under it when you sight through the mouthpiece, not halfway up from the windway floor to the windway ceiling.
You can use double sided tape to laminate something thin to the floor, ceiling or both, of the windway, as dictated by the windcutter blade position. Or you can use strips of aluminum metal duct tape (pure metal with an adhesive surface). You might find, two thicknesses of the aluminum tape is about right (that’s 0.01 inch). Or you might find that more is better. You can put all the layers of tape on the windway ceiling, some on the floor and some on the ceiling, or all on the floor, depending, again, on the position of the windcutter blade edge relative to the windway.
You’ll need something thin and stiff (I use a portable jigsaw blade with the teeth ground off) to strongly press each layer of aluminum tape into place.
The whistle will sound and play best if the surfaces of the windway are as perfectly uniform as possible and there’s just enough space for the air that’s needed to make music. More space makes a less responsive whistle and less musical, less focused timbre. Too little space, and the whistle will sound like it can’t get the music out. There’s a sweet spot where the voice really sings out, and then if you reduce the space more than that, it starts to sound muffled.
Best wishes,
Jerry
But I don’t have any of that. 
I used scissors and made it bigger again. Seems to have work.
Thanks.
If you provide me with a complete list of what you do have, I’ll suggest how you might use it to tweak a whistle.
Best wishes,
Jerry
P.S. BTW, I painted a refrigerator today. I always enjoy a chance to work in oils again.