Wierd ass mark on back formed after mosquito bite

So the other day I took a shirtless walk through the city and I got bit a lot by mosquitos (or atleast I think they were mosquitos) because I had lots of itchy bumps all over me.. but a couple days later and I’m noticing this mark on my back where a bite used to be .. anybody know what this is, the cause of it, or what it’s from ?? Thanks

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