Thanks for the query to ATD for an opinion,
This is likely to be a dermatitis singular nodule which is most likely allergic or due to contact dermatitis. This is a small papule, non painful, non inflamed and often non itchy. These are self limiting usually. Another differential could be an insect bite with a reactionary bleb formation and will require anti histaminic orally and a Soframycin cream application locally.
It should ideally subside in next 48 hrs, else you may show it to a dermatologist.
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