What is this?

It’s almost like a blister. She’s had it for a few days now. It’s not hot or even warm, it’s also not sore. I don’t want to take her to the dr for just a little red bump and have them look at me like I’m crazy. My husband also thinks I’m nuts lol. The only reason I’m worried is because it’s been there a few days. It hasn’t gotten worse or spread at all. At first I thought it was a bug bite, but I think a bug bite would have went away by now. What are your opinions?