Worst case scenario could be a fractured navicular bone. I fractured mine and literally described it the exact same way as you did. I really would advise making an appt with a doctor that will get you a CT scan or an MRI right away. Make your call sound urgent and get this appt ASAP. If possible, do not run until the appt. Trust me, you don't want to mess around with this type of fracture. It is incredibly slow healing due to lack of blood flow to the area.
Just to put some credibility to this story, I'll give you my history. Similar symptoms as you, never really killed but definitely felt funny. I went to the doctor in Sept. Was in a boot until November. Went to a new doctor when the 1st doc told me I hadn't healed at all since Sept. From Nov until Jan I was in a cast from the knee down using a bone stimulator. First month out of the cast I was in a boot. Then trying to get back to walking pain free followed by some PT brought me to April (late) when i could try to run again. I felt alright but probably should have waited longer. That summer I went back to the doc, found out my fracture only partially healed. The next October (so past the 1 year mark at htis point) I had surgery. I couldn't run until June, couldn't walk without a heavy limp for about a year. It took me a full year to be able to feel normal running (stride wise). I have two screws in my foot and have foot pain every day, every run. A real runner is tough enough to know when to back off something and see a doctor rather than letting your obsessive side kick in. Sorry if this scares you, but I hope you see someone and that my story does not become your own!