Thanks for the query.
It could be a post inflammatory swelling due to rigorous masturbation. Sometimes tissues can tear and cause bleeding leading to a small hematoma or a blood-filled swelling as well. Avoid masturbation or intercourse till it completely heals, do not apply any lotions, soaps or cosmetics over the area. Wear loose cotton undergarments and avoid tight fitting clothes. Also drink plenty of water. Anti-inflammatory medications for 3 days may help. In case there is no reduction in the size of swelling or you notice any bleeding, see a doctor in a week's time.
Hope this helped.
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