Hi... Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns... As per your complain swollen knee along with bruising is due to traumatic injury to the soft tissues leading to rupture of small blood vessels that are causing spillage of blood into the soft tissues causing formation of a hematoma and bruise. There is also accumulation of inflammatory cells, exudate, ruptured capillaries,fibres leading to swelling and at times hard area at the site of injury.. Nothing to worry you can do cold compresses over the swollen area for reducing swelling, apply a heparin containing gel for faster fading of bruise. Take anti-inflammatory painkiller like Ibuprofen for pain relief. Elevate your leg while lying on bed. The sores in mouth seems to be canker sores and you can do warm saline gargles, apply a numbing gel containing Choline salicylate over it and suck on ice pops.. Avoid spicy and hard foods. They will resolve within a week. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.