Answer:
They could be cause by a few things. It could be a bug bite. If you itched it, then bumps could form even more. It could also be an allergic reaction to something. (Hives, possibly. Even just on a small, isolated area, it can happen.) If it is part of a rash, it might be something like poison ivy or poison oak. It could be some ingrown hairs, depending on the area. You best bet - since it's itchy - would be a bug bite or reaction. Try a soothing, anti-itch cream. If you aren't sure or are concerned, see ac doctor. They could probably help.