It may be a bacterial infection or possible fungal infection. At this point clean the area well with antibacterial soap and apply some neosporin to the area. If this doesn't help within a couple of days, then see your doctor, you may need an antibiotic. You don't mention anything about pain, so keep an eye on the area as well just in case this may be related to a hernia (but at this point, I wouldn't think that) So just do the above and don't wear any tight clothing. Actually wear something loose or something that you can allow it to get air as well and keep clean.
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