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Yes, you should have it checked, though not urgently. You can try to see your family doctor tomorrow, and if not possible, go to an urgent care center. This could be blood, and the question is why? Your elbow needs to be xrayed and the swelling might need to be tapped with a needle for analysis and culture.
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This could also be a cyst, a sack full of clear fluid, which is typically benign and can be surgically removed, or just drained with the needle