Raised Bump On Neck- Bug Bite Or Not?

I have the same thing on my shoulder.I have looked all over the internet to figure out what it is. Some people thinks it's a jigger bite or a red bug bite, but I don't know. But I can't recall myself being outdoors only to walk my dog.

I have had something that may be similar. It was a bite on the back of my neck near the hair line that remained for some time and seemed to change to get better and then get worse. Sometimes it itched and sometimes not. One morning while laying awake in bed I watched a small black jumping spider travel across the ceiling to the wall down the wall to the bed. I killed it and the bump on my neck went away. Occasionally every few years I get a similar bump and when I discover it I use insect repellant on my neck and the bump is gone in two days. Since this theory is developing I have observed while in the checkout line at the grocery store that many people have a similar bump on their neck. It would be interesting to learn more about this.