If not plantars faciitis what could it be?

I have intense pain in Left heel. NOT convinced is Plantar fascitis as I am very flexible - no pain on doing recommended stretches. Pain when standing or pressing on heel. Also, includes interior side of heel, not just bottom of foot. Had a cortisone injection and now feels worse! (Had been very gradually improving). My symptoms don't seem to coincide with "plantar fascitis" cannot figure out what else it might be.