I generally seal wood, before applying stain, by adding a thin coat of shellac. Sealing the wood helps a great deal in keeping the stain(s) even. If the end product with be light in color I use blond shellac and if it's to be dark I opt for the garnet.
What DW said the only fix, given that you are working with pw is to overstain with dark colors, although you might be able to paint? If it were solid wood you could plane off a wee bit and start over.
It's always difficult to tell from pics but is it possible that you could have gotten some silicone on the stock or something like WD 40?
I make it a rule to go through my finishing steps with cut off stock before working on the final piece. You never know what's going to happen.
Finally, given that's it is pw, can you turn the project over?
Nice cut though, you deserve some 'atta boys'.