How do you fix green lightning bolt with a squiggle on apple watch?

Apple Support's article (link below) may help you check on the squiggle ... am not sure.

Status icons and symbols on Apple Watch - Apple Support

Seems the green lightning bolt just lets you know your Watch is charging.

See if Apple Support's articles can help you:

What to do: If your Apple Watch won't charge or it won't turn on - Apple Support

and

How to: Keep Apple Watch within acceptable operating temperatures - Apple Support

PS:

"You might notice that your device feels warmer when you Wirelessly charge your device

These conditions are normal, and your device will return to a regular temperature when the process is complete

If your device doesn't display a temperature warning, you can keep using your device."

Info. from: Apple support's article:

If your iPhone, iPad, or iPod touch gets too hot or too cold - Apple Support

Seems one fix that has worked for some, is to leave the watch battery to drain completely ,,, over a few days,

,,, until nothing happens when you press the side button ...

no red or green lightning symbol, just a blank screen ..

and then put on the charger for the 2.5 hours.

Mine is also a 7 and had gone thru an update 😒. I will try to leave on charger longer. Do or die. I got it for my 50th wedding anniversary in 2020. I have a pendant wind up watch that I got in 1968 still working. Guess it’s back to the windup.

Mine has the same but does not charge and gets very hot

You might want to try seeing if it will charge by plugging into a computer with the cable.

PS: If the Watch is totally drained, it can take a while to respond,