Fill up a bucket/bowl of lukewarm water. Make sure it's not too hot.
Add in 1 tbls of soft hair conditioner.
Soak the piece of clothing for 30 minutes and gently stretch the piece of clothing back to its original shape. Hand wash to rinse out the conditioner and lay flat to dry.
Soaking it in water will soften the fibers and they may become soft enough for you to pull your garment into something a little less shrunk. You can also iron it and tug it while it is wet and that may help to stretch it some. Many cottons are progressive shrinkers and need 3 or 4 trips thru the machine before they are finished shrinking. Your challenge may be in the construction of the garmet because not all the pieces are cut along the grain line and curved sections may be more willing to stretch. You've got nothing to lose by trying to revive your garment. Good luck.
The success in trying this without the seam stitching ripping and coming apart will also depend on the type of thread used to stitch the seams and to serge the seam allowances. Unfortunately, many ready-made garments are manufactured with thread that is either poor quality, or cotton thread that has not been pre-shrunk.
I have a plastic chair mat under my computer desk that the edges are curled and won't lay flat. Have been unable to bend them back as the plastic is hard
Can't do it.
https://www.wikihow.com/Unshrink-Clothes
https://www.rd.com/home/cleaning-organizing/how-to-un-shrink-clothes/
Soaking it in water will soften the fibers and they may become soft enough for you to pull your garment into something a little less shrunk. You can also iron it and tug it while it is wet and that may help to stretch it some. Many cottons are progressive shrinkers and need 3 or 4 trips thru the machine before they are finished shrinking. Your challenge may be in the construction of the garmet because not all the pieces are cut along the grain line and curved sections may be more willing to stretch. You've got nothing to lose by trying to revive your garment. Good luck.
Further to V Smith's helpful comment:
The success in trying this without the seam stitching ripping and coming apart will also depend on the type of thread used to stitch the seams and to serge the seam allowances. Unfortunately, many ready-made garments are manufactured with thread that is either poor quality, or cotton thread that has not been pre-shrunk.
I would try blocking it the same way you would block a sweater:
Thoroughly wet the shirt and stretch it as much as you can before laying it on a towel to air dry.
OR wet the shirt and iron it wet, stretching it while using a dry iron to iron it until it is totally dry.
Good luck!!!