The reasons for heel pain are varied. Most frequently, heel pain is due to a condition called plantar fasciitis, which is the inflammation of a long ligament on the bottom of your foot. Typically, the heel and/or arch hurts with the first few steps out of bed in the morning or after sitting for a while. Heel pain can also be due to nerve issues, trauma, and conditions such as rheumatoid arthritis.
This is an extremely common condition and is usually fixed through any number of conservative treatments such as stretching exercises, orthotics that support your arches, or antiinflammatory medications such as Advil.