A helicoil would work but it's not worth the cost in this case unless sourcing parts ends up being difficult because pandemic. If you look on the back side of the left crankarm, there should be a number stamped and my guess is it's 175 for the length of the arm. You can order a new left crankarm in the same length and don't need to match exact brand or model, but do need to match the orientation of the square taper interface. Replacing it will require a basic square taper crank puller and it's likely something you can do yourself. Make sure the pedal gets reinstalled with grease and it's tightened down pretty darn tight.
I wouldn't be in a rush to replace the crank. Cheap cranks tend to shift ok. The chainrings are often not replaceable so you can upgrade if and when they wear out or of you do a full drivetrain upgrade.