Pain in the left side of the lower back and upper buttocks usually refers to excessive strain on the sacroiliac joint, as well as the iliac pterygoid and posterior superior iliac spine, where there are muscle attachment points, or a sterile inflammatory lesion in the local soft tissues after getting cold, which will stimulate the peripheral nerves around the area and cause pain in this location. When this occurs, the first step should be to keep this location relaxed, rested and warm. If the soft tissues in this location continue to be tense, it can easily lead to continued irritation of the area where the inflammation occurs and can worsen the inflammatory edema. If it gets cold, it will cause the muscle tissues in this area to become tense and blood circulation will decrease, which will lead to more accumulation of metabolic products and cause the pain to become more pronounced. In addition, you should also apply warm water bags for hot compresses to increase blood circulation. You can also apply magnetic therapy patches to help improve local blood flow, and you can apply ointments that activate blood stasis and relieve tendons and channels, such as wound pain relief, which can also effectively improve local circulation and have the effect of reducing swelling and relieving pain.