Know Buddy is not a dachshund but something odd happened yesterday I was petting his head felt a little bump took him to the room with a brighter lite to see if it was a tick. Not a tick just a bump well this afternoon he came up to me has a hole about where the bump was looks like a red piece of meat sticking out ???? Anyone seen anything like this going to try for a picture too.
I wonder if he scratched it with his hind foot and broke it open. Maybe he got a little seed or sliver in there (or plugged hair follicle) and it filled up with fluid? Or a spider bite...Was the bump hard or squishy? As I'm sure you already know watch for it to come back and/or grow to check for mast cell. Hopefully it will heal up and go away fast!
Rudy has something similar on the very top of his head. He has had it for a couple years, and it came up fast. It was checked right away and just a growth, kind of like a mole.... and the last time he was in for teeth cleaning, they snipped it off, and it has grown back. Doesn't get any larger than it is now - looks about the size as your picture. I would have it looked at, just to be safe !