It is possible to unshrink wool that someone (not you, of course) popped into the dryer and is now small enough for little Bruiser to wear.
And pretty much all you'll need to do is help your sweater fibers relax, too, with a little help from baby shampoo worked gently into the fibers while washing it by hand.
Here's how to get the resizing process started.
Start by soaking the sweater in a sink or bucket full of warm water and about two tablespoons of baby shampoo.
This soapy soak will relax the wool fibers so that you can gently work it back into shape without breaking any of the wool fibers. About 15 minutes should be long enough.
Remove and rinse under cool running water to remove the soap, gently squeezing the garment starting at the top and working your way down.
Resist the urge to wring. That can cause the delicate wool fibers to break.
Roll the sweater in a towel to emove any lingering water from the wool before you begin the letting out process.
To unshrink wool gently stretch and pin it back into shape. To do this, pin the wool sweater to a large cork board, stretching the neck, arms, and sides as taut as possible without damaging the fibers. Let sit for at least an hour.
Return to re-stretch and re-pin your sweater every few hours. It will take several stretching and re-pinning sessions to unshrink a wool sweater.
But if you adore that wool garment, you'll be delighted with the results of your unshrinking efforts. And if needed, consider a how to wash clothes refresher course.