Heel pain is a common foot problem and has a number of possible causes. The most common cause is plantar fasciitis, which is inflammation where the plantar fascia attaches to the heel bone. The plantar fascia is a thick band of connective tissue that spans the sole of the foot and provides shock absorption while walking.
Might be useful to mention where you earned these degrees but generally in the US Bachelors = undergraduate and Masters = graduate. Post-graduate is kind of an umbrella term that might mean Masters/PhD but also might mean professional certification or maybe even something like continuing education.
Master's degree programs give advanced training to graduates of bachelor's programs in design and prepare those with other degrees for the profession. For example, Pratt Institute offers a Master of Science in interior design requiring 48 semester units beyond the bachelor's degree.