Bottom of back been sore and bruised for 8 weeks and can feel my bones when i press on it and looks swollen what could this be?

need more info: 8 weeks.How did it get bruised? If it was spontaneous, as a female, you may have ruptured an ovarian cyst and the blood is pulling in your back. If it is the lower lumbar spine, may be you have a compression fracture at that vertebra. Your initial evaluation should be to see your primary care physician and have him evaluate you. He/she may want to do an x-ray for starters.