What does the pain in the back bottom of the feet means with a little swelling.the pain is horrible with a pulsing sensation and pain even at rest...

Many possibilities: Heel pain could be due to different reasons, of which may include: trauma (fracture, tendon or ligamentous tear, arthritis), infection, metabolic conditions (gout) musculoskeletal or biomechanical abnormality, or neurologic conditions (neuropathy). A thorough history and physical exam and possibly laboratory and radiology exams could determine the cause. If symptoms persist get it evaluated.

See below: If you are referring to the back of the heel, then you may have achilles tendonitis, if on the bottom of the foot you may have plantar fasciitis.