does the bump look like this? http://www.dermnet.org.nz/viral/img/hsimplex2-s.jpg and turn into something a little like this? http://www.doctorspiller.com/images/Aids/HerpesWhitlow.jpg (don't be alarmed about 'Aids' in the url - this is NOT necessarily a symptom of HIV/AIDS!)
Those are pictures of herpes whitlow - that's the herpes virus on the skin of your hands; you can pick it up sometimes from sucking or biting your finger if you have a cold sore, or in some other ways too. You can treat it with herbal remedies like lysine or lemon balm, or get antiviral tablets or creams from your doctor if that's what it is.
Don't touch your or anyone else's eyes, mouth or genitals when you have the lump if it is that. If you want to know for sure you could go the doctor as soon as you get the lump and have it swabbed for the herpes virus. 'Herpes' sounds scary because people associate it with STIs but it's actually a really common virus and you can get it in all kinds of ways apart form sex.
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