If the forehead accidentally collides and a large bag appears, you can use cold compresses to quickly reduce the swelling within 24 hours of the appearance of the bag. The cold compress can make the hematoma inside the bag slowly subside and also soothe the local pain, after which you can apply an ointment that reduces swelling and pain and activates blood stasis. Depending on the degree of swelling of the bag, it can generally recover in about a week, during which time local hot compresses can also be applied to reduce swelling. If the pain is severe, topical pain relief ointment can be applied or oral anti-inflammatory drugs can be combined. If the symptoms have significantly subsided, no further treatment can be required, just pay attention to yourself and avoid re-injury to your forehead. If there is an increase in redness and swelling or other conditions such as headaches, which do not subside for a long time, it is recommended to go to the hospital for examination as soon as possible.