Q: This summer I had knobby squash. I know what old squash looks like. These are immature in size, young, not very fat, but the skin looks like we waited too long to pick it. Why?

A: This looks like squash bug damage. These insects are kin to stink bugs, The insert a sharp “nose” into young fruit and make bumps and knobs on the skin.

To control them, use a product labeled for garden insect control like acetamiprid (click for sources) or cyfluthrin (click for sources)

Other, mostly organic controls, include these garden insecticides (click for sources)

See also

Squash Bug Identification

Squash Bug