Pain is present after an injury due to inflammation - the body's response to an injury. The swelling is probably caused by tiny broken blood vessels and squashed tissue cells burst in the injury.
If it hurts to take a deep breath, this could indicate a broken rib or breastbone. You could get...
Of course you can eat them. Garden mushroom is one of the best delicacies and the best part is they are literally at no cost to you. Fry them in olive oil, together with other vegetables and they will make a fantastic meal.