What should you know about a blue-green lump under skin?

Blue-green colour often reflects blood changing beneath the skin as a bruise settles, especially after pressure or an unnoticed knock. A raised lump may instead be an inflamed follicle, boil, cyst, or a growth involving the skin. The surface may look blue-green while the deeper lump feels soft, firm, or mobile. These features can overlap, and colour cannot establish a diagnosis. Record its location, size, tenderness, warmth, firmness, and whether the overlying skin is broken.

Do not massage, squeeze, or puncture the lump. Take dated photographs in consistent light and avoid clothing or equipment that presses on it. If it followed minor trauma and the skin is closed, a wrapped cold pack may ease early discomfort; later, gentle warmth may feel soothing. Arrange a clinician review if it remains or changes. For selected inflamed lumps, treatment may include an injection into the lesion, but that decision follows an examination.

Get prompt care for rapid enlargement, increasing warmth, spreading redness, pus, severe pain, fever, or difficulty moving the nearby area. Have a persistent or unexplained lump assessed if it becomes hard, fixed, ulcerated, crusted, or bleeds. A sore that does not heal or repeatedly breaks down also needs review; a clinician may need to distinguish infection from a non-infectious skin growth.

Could this be a resolving bruise, boil, cyst, or another growth? Does the depth or mobility change the assessment? Should it be monitored, treated for inflammation, or sampled? What signs of infection or skin breakdown should bring me back sooner?