Squash – Bumpy Skin
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.
Other, mostly organic controls, include these garden insecticides (click for sources)