Vine crops, including pumpkins, are subject to various leaf spot diseases.  However, it's often difficult to determine what disease, if any, is present by viewing photos and sometimes laboratory analysis is needed to do it. 

Spots can also be caused by insect damage, a bit of hail, strong wind, or other abrasion.  

We don't know what's causing the spots on the leaf shown in the photo.  The damage is inconsequential at this point, and unless it progresses rapidly, it can be ignored. 

Following is more information about leaf spots on vine crops and how to deal with diseases in the vegetable garden:

https://apps.extension.umn.edu/garden/diagnose/plant/vegetable/wintersquash/leavesspots.html

https://extension.umn.edu/planting-and-growing-guides/managing-plant-diseases-home-garden