Hi, Welcome to HealthcareMagic forum. It is most likely a trauma induced bruise which should resolve spontaneously with warm compresses and analgesics (motrin). But if you are sure there was no injuries sustained spontaneous bruise with soreness could be related to - Allergic response - Reactions to any drugs consumed - bleeding diathesis You need not be concerned now. Apply compresses over the affected region. Avoid aspirin. You may use alternative non steroidal anti-inflammatory drugs such as motrin if the pain is severe and you are not allergic to it. Watch over the bruise for few days. You should gradually recovery. But if it persists or worsen visit your doctor for detailed clinical examination and evaluation. Hope this helps. Wish you a speedy recovery. Warm Regards