Looks like some sort of leaf gall to me.

https://extension.umn.edu/yard-and-garden-insects/insect-and-mite-galls

maybe aphid eggs?

I'm probably incorrect, maybe someone will know the right answer

Need a better picture to be sure.

Drastic rapid changes in temperature combined with wet soils can cause those types of lesions. The plant can not adapt fast enough and it causes the cells to burst. They usually form on older leaves as the cell walls are stiffer.