Hi, The sudden appearance of a lump on the shin along with red discoloration, hot stinging pain, and itching could be a sign of an infection or an allergic reaction. It is important to seek medical attention as soon as possible, especially if the symptoms are worsening or spreading. The lump could be an abscess or a boil, which is a localized infection that can cause redness, swelling, and pain. It is important to have it evaluated by a healthcare provider, who may need to drain the abscess and prescribe antibiotics to treat the infection. The red discoloration and itching could also be a sign of an allergic reaction, which can be caused by a variety of factors such as insect bites, medication, or exposure to certain substances. If you suspect an allergic reaction, seek medical attention right away, especially if you have difficulty breathing or swelling of the face or throat. In summary, it is important to seek medical attention for a sudden lump on the shin along with red discoloration, hot stinging pain, and itching. A healthcare provider can evaluate the symptoms and recommend appropriate treatment to prevent complications. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Priyanka, General & Family Physician