I would be interested to know if you take a lot of aspirin, are on blood thinners, take vitamin E, or fish oil supplements. All of these can cause increased clotting time and can result in bleeding under the skin (bruising) called a hematoma. No big deal except it may mean something is wrong with your clotting time. You may not even have hit or injured your finger noticably, but still the bleeding into the surrounding tissue causes the swelling and discoloration. It will go away, but keep an eye out for other areas on your body that bruises may have formed without any major injury that you are aware of. If you see these bruises, see a doctor and have blood tests (coagulation studies) to make sure you are clotting properly.
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