Stretched knitting

I have made a mistake with the jumper I have been knitting for weeks. I ironed the panel before stitching them together and they have stretched. Has anybody got any ideas on how I can reshape them. Many thanks

Greetings and welcome!!!

What kind of fiber is your yarn made of?? Usually man made fibers can’t be reshaped. But some natural ones can be redone.

Knitcindy